Protocol

Heads up! This article is about the protocol for the latest stable release of Minecraft Java Edition (1.19.3, protocol 761). For the Java Edition pre-releases, see Pre-release protocol. For the incomplete Bedrock Edition docs, see Bedrock Protocol. For the old Pocket Edition, see Pocket Edition Protocol Documentation.

This page presents a dissection of the current Minecraft protocol.

If you're having trouble, check out the FAQ or ask for help in the IRC channel #mcdevs on irc.libera.chat (More Information).

Note: While you may use the contents of this page without restriction to create servers, clients, bots, etc; substantial reproductions of this page must be attributed IAW CC BY-SA 4.0.

The changes between versions may be viewed at Protocol History.

Definitions

The Minecraft server accepts connections from TCP clients and communicates with them using packets. A packet is a sequence of bytes sent over the TCP connection. The meaning of a packet depends both on its packet ID and the current state of the connection. The initial state of each connection is Handshaking, and state is switched using the packets Handshake and Login Success.

Data types

All data sent over the network (except for VarInt and VarLong) is big-endian, that is the bytes are sent from most significant byte to least significant byte. The majority of everyday computers are little-endian, therefore it may be necessary to change the endianness before sending data over the network.

Name	Size (bytes)	Encodes	Notes
Boolean	1	Either false or true	True is encoded as 0x01, false as 0x00.
Byte	1	An integer between -128 and 127	Signed 8-bit integer, two's complement
Unsigned Byte	1	An integer between 0 and 255	Unsigned 8-bit integer
Short	2	An integer between -32768 and 32767	Signed 16-bit integer, two's complement
Unsigned Short	2	An integer between 0 and 65535	Unsigned 16-bit integer
Int	4	An integer between -2147483648 and 2147483647	Signed 32-bit integer, two's complement
Long	8	An integer between -9223372036854775808 and 9223372036854775807	Signed 64-bit integer, two's complement
Float	4	A single-precision 32-bit IEEE 754 floating point number
Double	8	A double-precision 64-bit IEEE 754 floating point number
String (n)	≥ 1 ≤ (n×3) + 3	A sequence of Unicode scalar values	UTF-8 string prefixed with its size in bytes as a VarInt. Maximum length of n characters, which varies by context. The encoding used on the wire is regular UTF-8, not Java's "slight modification". However, the length of the string for purposes of the length limit is its number of UTF-16 code units, that is, scalar values > U+FFFF are counted as two. Up to n × 3 bytes can be used to encode a UTF-8 string comprising n code units when converted to UTF-16, and both of those limits are checked. Maximum n value is 32767. The + 3 is due to the max size of a valid length VarInt.
Text Component	Varies	See Text formatting#Text components	Encoded as a NBT Tag, with the type of tag used depending on the case: As a String Tag: For components only containing text (no styling, no events etc.). As a Compound Tag: Every other case.
JSON Text Component	≥ 1 ≤ (262144×3) + 3	See Text formatting#Text components	The maximum permitted length when decoding is 262144, but the Notchian server since 1.20.3 refuses to encode longer than 32767. This may be a bug.
Identifier	≥ 1 ≤ (32767×3) + 3	See Identifier below	Encoded as a String with max length of 32767.
VarInt	≥ 1 ≤ 5	An integer between -2147483648 and 2147483647	Variable-length data encoding a two's complement signed 32-bit integer; more info in their section
VarLong	≥ 1 ≤ 10	An integer between -9223372036854775808 and 9223372036854775807	Variable-length data encoding a two's complement signed 64-bit integer; more info in their section
Entity Metadata	Varies	Miscellaneous information about an entity	See Entity_metadata#Entity Metadata Format
Slot	Varies	An item stack in an inventory or container	See Slot Data
NBT	Varies	Depends on context	See NBT
Position	8	An integer/block position: x (-33554432 to 33554431), z (-33554432 to 33554431), y (-2048 to 2047)	x as a 26-bit integer, followed by z as a 26-bit integer, followed by y as a 12-bit integer (all signed, two's complement). See also the section below.
Angle	1	A rotation angle in steps of 1/256 of a full turn	Whether or not this is signed does not matter, since the resulting angles are the same.
UUID	16	A UUID	Encoded as an unsigned 128-bit integer (or two unsigned 64-bit integers: the most significant 64 bits and then the least significant 64 bits)
BitSet	Varies	See #BitSet below	A length-prefixed bit set.
Fixed BitSet (n)	ceil(n / 8)	See #Fixed BitSet below	A bit set with a fixed length of n bits.
Optional X	0 or size of X	A field of type X, or nothing	Whether or not the field is present must be known from the context.
Array of X	count times size of X	Zero or more fields of type X	The count must be known from the context.
X Enum	size of X	A specific value from a given list	The list of possible values and how each is encoded as an X must be known from the context. An invalid value sent by either side will usually result in the client being disconnected with an error or even crashing.
Byte Array	Varies	Depends on context	This is just a sequence of zero or more bytes, its meaning should be explained somewhere else, e.g. in the packet description. The length must also be known from the context.
ID or X	size of VarInt + (size of X or 0)	See #ID or X below	Either a registry ID or an inline data definition of type X.
ID Set	Varies	See #ID Set below	Set of registry IDs specified either inline or as a reference to a tag.
Sound Event	Varies	See #Sound Event below	Parameters for a sound event.

Identifier

Identifiers are a namespaced location, in the form of minecraft:thing. If the namespace is not provided, it defaults to minecraft (i.e. thing is minecraft:thing). Custom content should always be in its own namespace, not the default one. Both the namespace and value can use all lowercase alphanumeric characters (a-z and 0-9), dot (.), dash (-), and underscore (_). In addition, values can use slash (/). The naming convention is lower_case_with_underscores. More information. For ease of determining whether a namespace or value is valid, here are regular expressions for each:

• Namespace: [a-z0-9.-_]
• Value: [a-z0-9.-_/]

VarInt and VarLong

Variable-length format such that smaller numbers use fewer bytes. These are very similar to Protocol Buffer Varints: the 7 least significant bits are used to encode the value and the most significant bit indicates whether there's another byte after it for the next part of the number. The least significant group is written first, followed by each of the more significant groups; thus, VarInts are effectively little endian (however, groups are 7 bits, not 8).

VarInts are never longer than 5 bytes, and VarLongs are never longer than 10 bytes. Within these limits, unnecessarily long encodings (e.g. 81 00 to encode 1) are allowed.

Pseudocode to read and write VarInts and VarLongs:

private static final int SEGMENT_BITS = 0x7F;
private static final int CONTINUE_BIT = 0x80;

public int readVarInt() {
    int value = 0;
    int position = 0;
    byte currentByte;

    while (true) {
        currentByte = readByte();
        value |= (currentByte & SEGMENT_BITS) << position;

        if ((currentByte & CONTINUE_BIT) == 0) break;

        position += 7;

        if (position >= 32) throw new RuntimeException("VarInt is too big");
    }

    return value;
}

public long readVarLong() {
    long value = 0;
    int position = 0;
    byte currentByte;

    while (true) {
        currentByte = readByte();
        value |= (long) (currentByte & SEGMENT_BITS) << position;

        if ((currentByte & CONTINUE_BIT) == 0) break;

        position += 7;

        if (position >= 64) throw new RuntimeException("VarLong is too big");
    }

    return value;
}

public void writeVarInt(int value) {
    while (true) {
        if ((value & ~SEGMENT_BITS) == 0) {
            writeByte(value);
            return;
        }

        writeByte((value & SEGMENT_BITS) | CONTINUE_BIT);

        // Note: >>> means that the sign bit is shifted with the rest of the number rather than being left alone
        value >>>= 7;
    }
}

public void writeVarLong(long value) {
    while (true) {
        if ((value & ~((long) SEGMENT_BITS)) == 0) {
            writeByte(value);
            return;
        }

        writeByte((value & SEGMENT_BITS) | CONTINUE_BIT);

        // Note: >>> means that the sign bit is shifted with the rest of the number rather than being left alone
        value >>>= 7;
    }
}

Note Minecraft's VarInts are identical to LEB128 with the slight change of throwing a exception if it goes over a set amount of bytes.

Note that Minecraft's VarInts are not encoded using Protocol Buffers; it's just similar. If you try to use Protocol Buffers Varints with Minecraft's VarInts, you'll get incorrect results in some cases. The major differences:

• Minecraft's VarInts are all signed, but do not use the ZigZag encoding. Protocol buffers have 3 types of Varints: uint32 (normal encoding, unsigned), sint32 (ZigZag encoding, signed), and int32 (normal encoding, signed). Minecraft's are the int32 variety. Because Minecraft uses the normal encoding instead of ZigZag encoding, negative values always use the maximum number of bytes.
• Minecraft's VarInts are never longer than 5 bytes and its VarLongs will never be longer than 10 bytes, while Protocol Buffer Varints will always use 10 bytes when encoding negative numbers, even if it's an int32.

Sample VarInts:

Value	Hex bytes	Decimal bytes
0	0x00	0
1	0x01	1
2	0x02	2
127	0x7f	127
128	0x80 0x01	128 1
255	0xff 0x01	255 1
25565	0xdd 0xc7 0x01	221 199 1
2097151	0xff 0xff 0x7f	255 255 127
2147483647	0xff 0xff 0xff 0xff 0x07	255 255 255 255 7
-1	0xff 0xff 0xff 0xff 0x0f	255 255 255 255 15
-2147483648	0x80 0x80 0x80 0x80 0x08	128 128 128 128 8

Sample VarLongs:

Value	Hex bytes	Decimal bytes
0	0x00	0
1	0x01	1
2	0x02	2
127	0x7f	127
128	0x80 0x01	128 1
255	0xff 0x01	255 1
2147483647	0xff 0xff 0xff 0xff 0x07	255 255 255 255 7
9223372036854775807	0xff 0xff 0xff 0xff 0xff 0xff 0xff 0xff 0x7f	255 255 255 255 255 255 255 255 127
-1	0xff 0xff 0xff 0xff 0xff 0xff 0xff 0xff 0xff 0x01	255 255 255 255 255 255 255 255 255 1
-2147483648	0x80 0x80 0x80 0x80 0xf8 0xff 0xff 0xff 0xff 0x01	128 128 128 128 248 255 255 255 255 1
-9223372036854775808	0x80 0x80 0x80 0x80 0x80 0x80 0x80 0x80 0x80 0x01	128 128 128 128 128 128 128 128 128 1

Position

Note: What you are seeing here is the latest version of the Data types article, but the position type was different before 1.14.

64-bit value split into three signed integer parts:

• x: 26 MSBs
• z: 26 middle bits
• y: 12 LSBs

For example, a 64-bit position can be broken down as follows:

Example value (big endian): 01000110000001110110001100 10110000010101101101001000 001100111111

• The red value is the X coordinate, which is 18357644 in this example.
  
• The blue value is the Z coordinate, which is -20882616 in this example.
  
• The green value is the Y coordinate, which is 831 in this example.
  

Encoded as follows:

((x & 0x3FFFFFF) << 38) | ((z & 0x3FFFFFF) << 12) | (y & 0xFFF)

And decoded as:

val = read_long();
x = val >> 38;
y = val << 52 >> 52;
z = val << 26 >> 38;

Note: The above assumes that the right shift operator sign extends the value (this is called an arithmetic shift), so that the signedness of the coordinates is preserved. In many languages, this requires the integer type of val to be signed. In the absence of such an operator, the following may be useful:

if x >= 1 << 25 { x -= 1 << 26 }
if y >= 1 << 11 { y -= 1 << 12 }
if z >= 1 << 25 { z -= 1 << 26 }

Fixed-point numbers

Some fields may be stored as fixed-point numbers, where a certain number of bits represent the signed integer part (number to the left of the decimal point) and the rest represent the fractional part (to the right). Floating point numbers (float and double), in contrast, keep the number itself (mantissa) in one chunk, while the location of the decimal point (exponent) is stored beside it. Essentially, while fixed-point numbers have lower range than floating point numbers, their fractional precision is greater for higher values.

Prior to version 1.9 a fixed-point format with 5 fraction bits and 27 integer bits was used to send entity positions to the client. Some uses of fixed point remain in modern versions, but they differ from that format.

Most programming languages lack support for fractional integers directly, but you can represent them as integers. The following C or Java-like pseudocode converts a double to a fixed-point integer with n fraction bits:

 x_fixed = (int)(x_double * (1 << n));

And back again:

 x_double = (double)x_fixed / (1 << n);

Bit sets

The types BitSet and Fixed BitSet represent packed lists of bits. The Notchian implementation uses Java's BitSet class.

BitSet

Bit sets of type BitSet are prefixed by their length in longs.

Field Name	Field Type	Meaning
Length	VarInt	Number of longs in the following array. May be 0 (if no bits are set).
Data	Array of Long	A packed representation of the bit set as created by BitSet.toLongArray.

The ith bit is set when (Data[i / 64] & (1 << (i % 64))) != 0, where i starts at 0.

Fixed BitSet

Bit sets of type Fixed BitSet (n) have a fixed length of n bits, encoded as ceil(n / 8) bytes. Note that this is different from BitSet, which uses longs.

Field Name	Field Type	Meaning
Data	Byte Array (n)	A packed representation of the bit set as created by BitSet.toByteArray, padded with zeroes at the end to fit the specified length.

The ith bit is set when (Data[i / 8] & (1 << (i % 8))) != 0, where i starts at 0. This encoding is not equivalent to the long array in BitSet.

Registry references

ID or X

Represents a data record of type X, either inline, or by reference to a registry implied by context.

Field Name	Field Type	Meaning
ID	VarInt	0 if value of type X is given inline; otherwise registry ID + 1.
Value	Optional X	Only present if ID is 0.

ID Set

Represents a set of IDs in a certain registry (implied by context), either directly (enumerated IDs) or indirectly (tag name).

Field Name	Field Type	Meaning
Type	VarInt	Value used to determine the data that follows. It can be either: 0 - Represents a named set of IDs defined by a tag. Anything else - Represents an ad-hoc set of IDs enumerated inline.
Tag Name	Optional Identifier	The registry tag defining the ID set. Only present if Type is 0.
IDs	Optional Array of VarInt	An array of registry IDs. Only present if Type is not 0. The size of the array is equal to Type - 1.

Registry data

These types are commonly used in conjuction with ID or X to specify custom data inline.

Sound Event

Describes a sound that can be played.

Name	Type	Description
Sound Name	Identifier
Has Fixed Range	Boolean	Whether this sound has a fixed range, as opposed to a variable volume based on distance.
Fixed Range	Optional Float	The maximum range of the sound. Only present if Has Fixed Range is true.

Other definitions

Term	Definition
Player	When used in the singular, Player always refers to the client connected to the server.
Entity	Entity refers to any item, player, mob, minecart or boat etc. See the Minecraft Wiki article for a full list.
EID	An EID — or Entity ID — is a 4-byte sequence used to identify a specific entity. An entity's EID is unique on the entire server.
XYZ	In this document, the axis names are the same as those shown in the debug screen (F3). Y points upwards, X points east, and Z points south.
Meter	The meter is Minecraft's base unit of length, equal to the length of a vertex of a solid block. The term “block” may be used to mean “meter” or “cubic meter”.
Global palette	A table/dictionary/palette mapping nonnegative integers to block states. Block state IDs are created in a linear fashion based off of order of assignment. One block state ID allocated for each unique block state for a block; if a block has multiple properties then the number of allocated states is the product of the number of values for each property. A current list of properties and state ID ranges is found on burger. Alternatively, the vanilla server now includes an option to export the current block state ID mapping, by running java -cp minecraft_server.jar net.minecraft.data.Main --reports. See Data Generators for more information.
Notchian	The official implementation of vanilla Minecraft as developed and released by Mojang.
Sequence	The action number counter for local block changes, incremented by one when clicking a block with a hand, right clicking an item, or starting or finishing digging a block. Counter handles latency to avoid applying outdated block changes to the local world. Also is used to revert ghost blocks created when placing blocks, using buckets, or breaking blocks.

Packet format

Packets cannot be larger than 2²¹ − 1 or 2097151 bytes (the maximum that can be sent in a 3-byte VarInt). For compressed packets, this applies to both the compressed length and uncompressed lengths.

Without compression

Field Name	Field Type	Notes
Length	VarInt	Length of Packet ID + Data
Packet ID	VarInt
Data	Byte Array	Depends on the connection state and packet ID, see the sections below

With compression

Once a Set Compression packet (with a non-negative threshold) is sent, zlib compression is enabled for all following packets. The format of a packet changes slightly to include the size of the uncompressed packet.

Compressed?	Field Name	Field Type	Notes
No	Packet Length	VarInt	Length of Data Length + compressed length of (Packet ID + Data)
No	Data Length	VarInt	Length of uncompressed (Packet ID + Data) or 0
Yes	Packet ID	VarInt	zlib compressed packet ID (see the sections below)
	Data	Byte Array	zlib compressed packet data (see the sections below)

If the size of the buffer containing the packet data and ID (as a VarInt) is smaller than the threshold specified in the packet Set Compression. It will be sent as uncompressed. This is done by setting the data length as 0. (Comparable to sending a non-compressed format with an extra 0 between the length, and packet data).

If it's larger than the threshold, then it follows the regular compressed protocol format.

Compression can be disabled by sending the packet Set Compression with a negative Threshold, or not sending the Set Compression packet at all.

Handshaking

Clientbound

There are no clientbound packets in the Handshaking state, since the protocol immediately switches to a different state after the client sends the first packet.

Serverbound

Handshake

This causes the server to switch into the target state.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x00	Handshaking	Server	Protocol Version	VarInt	See protocol version numbers (currently 760 in Minecraft 1.19.2).
			Server Address	String (255)	Hostname or IP, e.g. localhost or 127.0.0.1, that was used to connect. The Notchian server does not use this information. Note that SRV records are a simple redirect, e.g. if _minecraft._tcp.example.com points to mc.example.org, users connecting to example.com will provide example.org as server address in addition to connecting to it.
			Server Port	Unsigned Short	Default is 25565. The Notchian server does not use this information.
			Next State	VarInt Enum	1 for Status, 2 for Login.

Legacy Server List Ping

This packet uses a nonstandard format. It is never length-prefixed, and the packet ID is an Unsigned Byte instead of a VarInt.

While not technically part of the current protocol, legacy clients may send this packet to initiate Server List Ping, and modern servers should handle it correctly. The format of this packet is a remnant of the pre-Netty age, before the switch to Netty in 1.7 brought the standard format that is recognized now. This packet merely exists to inform legacy clients that they can't join our modern server.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0xFE	Handshaking	Server	Payload	Unsigned Byte	always 1 (0x01).

See Server List Ping#1.6 for the details of the protocol that follows this packet.

Status

Main article: Server List Ping

Clientbound

Status Response

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x00	Status	Client
			JSON Response	String (32767)	See Server List Ping#Response; as with all strings this is prefixed by its length as a VarInt.

Ping Response

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x01	Status	Client	Payload	Long	Should be the same as sent by the client.

Serverbound

Status Request

The status can only be requested once immediately after the handshake, before any ping. The server won't respond otherwise.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x00	Status	Server	no fields

Ping Request

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x01	Status	Server	Payload	Long	May be any number. Notchian clients use a system-dependent time value which is counted in milliseconds.

Login

The login process is as follows:

1. C→S: Handshake with Next State set to 2 (login)
2. C→S: Login Start
3. S→C: Encryption Request
4. Client auth
5. C→S: Encryption Response
6. Server auth, both enable encryption
7. S→C: Set Compression (optional)
8. S→C: Login Success

Set Compression, if present, must be sent before Login Success. Note that anything sent after Set Compression must use the Post Compression packet format.

For unauthenticated ("cracked"/offline-mode) and integrated servers (either of the two conditions is enough for an unencrypted connection) there is no encryption. In that case Login Start is directly followed by Login Success. The Notchian server uses UUID v3 for offline player UUIDs, with the namespace “OfflinePlayer” and the value as the player’s username. For example, Notch’s offline UUID would be derived from the string “OfflinePlayer:Notch”. This is not a requirement however, the UUID may be anything.

See Protocol Encryption for details.

Clientbound

Disconnect (login)

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x00	Login	Client	Reason	Chat	The reason why the player was disconnected.

Encryption Request

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x01	Login	Client	Server ID	String (20)	Appears to be empty.
			Public Key Length	VarInt	Length of Public Key
			Public Key	Byte Array	The server's public key, in bytes.
			Verify Token Length	VarInt	Length of Verify Token. Always 4 for Notchian servers.
			Verify Token	Byte Array	A sequence of random bytes generated by the server.

See Protocol Encryption for details.

Login Success

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x02	Login	Client	UUID		UUID
			Username		String (16)
			Number Of Properties		VarInt		Number of elements in the following array.
			Property	Name	Array	String (32767)
				Value		String (32767)
				Is Signed		Boolean
				Signature		Optional String (32767)	Only if Is Signed is true.

This packet switches the connection state to play.

The (notchian) server might take a bit to fully transition to the Play state, so it's recommended to wait for the Login (play) packet from the server.

The notchian client doesn't send any packets until the Login (play) packet.

Set Compression

Enables compression. If compression is enabled, all following packets are encoded in the compressed packet format. Negative values will disable compression, meaning the packet format should remain in the uncompressed packet format. However, this packet is entirely optional, and if not sent, compression will also not be enabled (the notchian server does not send the packet when compression is disabled).

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x03	Login	Client	Threshold	VarInt	Maximum size of a packet before it is compressed.

Login Plugin Request

Used to implement a custom handshaking flow together with Login Plugin Response.

Unlike plugin messages in "play" mode, these messages follow a lock-step request/response scheme, where the client is expected to respond to a request indicating whether it understood. The notchian client always responds that it hasn't understood, and sends an empty payload.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x04	Login	Client	Message ID	VarInt	Generated by the server - should be unique to the connection.
			Channel	Identifier	Name of the plugin channel used to send the data.
			Data	Byte Array (1048576)	Any data, depending on the channel. The length of this array must be inferred from the packet length.

In Notchian client, the maximum data length is 1048576 bytes.

Serverbound

Login Start

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x00	Login	Server	Name	String (16)	Player's Username.
			Has Sig Data	Boolean	Whether or not the next 5 fields should be sent.
			Timestamp	Long	When the key data will expire. Optional. Only sent if Has Sig Data is true.
			Public Key Length	VarInt	Length of Public Key. Optional. Only sent if Has Sig Data is true.
			Public Key	Byte Array	The encoded bytes of the public key the client received from Mojang. Optional. Only sent if Has Sig Data is true.
			Signature Length	VarInt	Length of Signature. Optional. Only sent if Has Sig Data is true.
			Signature	Byte Array	The bytes of the public key signature the client received from Mojang. Optional. Only sent if Has Sig Data is true.
			Has Player UUID	Boolean	Whether or not the next field should be sent.
			Player UUID	UUID	The UUID of the player logging in. Optional. Only sent if Has Player UUID is true.

Encryption Response

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x01	Login	Server	Shared Secret Length	VarInt	Length of Shared Secret.
			Shared Secret	Byte Array	Shared Secret value, encrypted with the server's public key.
			Has Verify Token	Boolean	Whether or not the Verify Token should be sent. If not, then the salt and signature will be sent.
			Optional Verify Token Length	VarInt	Length of Verify Token. Optional and only sent if Has Verify Token is true.
			Optional Verify Token	Byte Array	Verify Token value, encrypted with the same public key as the shared secret. Optional and only sent if Has Verify Token is true.
			Optional Salt	Long	Cryptography, used for validating the message signature. Optional and only sent if Has Verify Token is false.
			Optional Message Signature Length	VarInt	Array Length. Optional and only sent if Has Verify Token is false.
			Optional Message Signature	Byte Array	The bytes of the public key signature the client received from Mojang. Optional and only sent if Has Verify Token is false.

See Protocol Encryption for details. See Mojang_API#Player_Certificates for an API to get the message signature.

Login Plugin Response

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x02	Login	Server	Message ID	VarInt	Should match ID from server.
			Successful	Boolean	true if the client understood the request, false otherwise. When false, no payload follows.
			Data	Optional Byte Array (1048576)	Any data, depending on the channel. The length of this array must be inferred from the packet length.

In Notchian server, the maximum data length is 1048576 bytes.

Play

Clientbound

Spawn Entity

Sent by the server when a vehicle or other non-living entity is created.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x00	Play	Client	Entity ID	VarInt	A unique integer ID mostly used in the protocol to identify the entity.
			Entity UUID	UUID	A unique identifier that is mostly used in persistence and places where the uniqueness matters more.
			Type	VarInt	The type of the entity (see "type" field of the list of Mob types).
			X	Double
			Y	Double
			Z	Double
			Pitch	Angle	To get the real pitch, you must divide this by (256.0F / 360.0F)
			Yaw	Angle	To get the real yaw, you must divide this by (256.0F / 360.0F)
			Head Yaw	Angle	Only used by living entities, where the head of the entity may differ from the general body rotation.
			Data	VarInt	Meaning dependent on the value of the Type field, see Object Data for details.
			Velocity X	Short	Same units as Set Entity Velocity.
			Velocity Y	Short
			Velocity Z	Short

Spawn Experience Orb

Spawns one or more experience orbs.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x01	Play	Client	Entity ID	VarInt
			X	Double
			Y	Double
			Z	Double
			Count	Short	The amount of experience this orb will reward once collected.

Spawn Player

This packet is sent by the server when a player comes into visible range, not when a player joins.

This packet must be sent after the Player Info packet that adds the player data for the client to use when spawning a player. If the Player Info for the player spawned by this packet is not present when this packet arrives, Notchian clients will not spawn the player entity. The Player Info packet includes skin/cape data.

Servers can, however, safely spawn player entities for players not in visible range. The client appears to handle it correctly.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x02	Play	Client	Entity ID	VarInt	A unique integer ID mostly used in the protocol to identify the player.
			Player UUID	UUID	See below for notes on offline mode and NPCs.
			X	Double
			Y	Double
			Z	Double
			Yaw	Angle
			Pitch	Angle

When in online mode, the UUIDs must be valid and have valid skin blobs. In offline mode, UUID v3 is used with the String OfflinePlayer:<player name>, encoded in UTF-8 (and case-sensitive). The Notchian server uses UUID.nameUUIDFromBytes, implemented by OpenJDK here.

For NPCs UUID v2 should be used. Note:

<+Grum> i will never confirm this as a feature you know that :)

In an example UUID, xxxxxxxx-xxxx-Yxxx-xxxx-xxxxxxxxxxxx, the UUID version is specified by Y. So, for UUID v3, Y will always be 3, and for UUID v2, Y will always be 2.

Entity Animation (clientbound)

Sent whenever an entity should change animation.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x03	Play	Client	Entity ID	VarInt	Player ID.
			Animation	Unsigned Byte	Animation ID (see below).

Animation can be one of the following values:

ID	Animation
0	Swing main arm
1	Take damage
2	Leave bed
3	Swing offhand
4	Critical effect
5	Magic critical effect

Award Statistics

Sent as a response to Client Command (id 1). Will only send the changed values if previously requested.

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x04	Play	Client	Count		VarInt		Number of elements in the following array.
			Statistic	Category ID	Array	VarInt	See below.
				Statistic ID		VarInt	See below.
				Value		VarInt	The amount to set it to.

Categories (these are namespaced, but with : replaced with .):

Name	ID	Registry
minecraft.mined	0	Blocks
minecraft.crafted	1	Items
minecraft.used	2	Items
minecraft.broken	3	Items
minecraft.picked_up	4	Items
minecraft.dropped	5	Items
minecraft.killed	6	Entities
minecraft.killed_by	7	Entities
minecraft.custom	8	Custom

Blocks, Items, and Entities use block (not block state), item, and entity ids.

Custom has the following (unit only matters for clients):

Name	ID	Unit
minecraft.leave_game	0	None
minecraft.play_one_minute	1	Time
minecraft.time_since_death	2	Time
minecraft.time_since_rest	3	Time
minecraft.sneak_time	4	Time
minecraft.walk_one_cm	5	Distance
minecraft.crouch_one_cm	6	Distance
minecraft.sprint_one_cm	7	Distance
minecraft.walk_on_water_one_cm	8	Distance
minecraft.fall_one_cm	9	Distance
minecraft.climb_one_cm	10	Distance
minecraft.fly_one_cm	11	Distance
minecraft.walk_under_water_one_cm	12	Distance
minecraft.minecart_one_cm	13	Distance
minecraft.boat_one_cm	14	Distance
minecraft.pig_one_cm	15	Distance
minecraft.horse_one_cm	16	Distance
minecraft.aviate_one_cm	17	Distance
minecraft.swim_one_cm	18	Distance
minecraft.strider_one_cm	19	Distance
minecraft.jump	20	None
minecraft.drop	21	None
minecraft.damage_dealt	22	Damage
minecraft.damage_dealt_absorbed	23	Damage
minecraft.damage_dealt_resisted	24	Damage
minecraft.damage_taken	25	Damage
minecraft.damage_blocked_by_shield	26	Damage
minecraft.damage_absorbed	27	Damage
minecraft.damage_resisted	28	Damage
minecraft.deaths	29	None
minecraft.mob_kills	30	None
minecraft.animals_bred	31	None
minecraft.player_kills	32	None
minecraft.fish_caught	33	None
minecraft.talked_to_villager	34	None
minecraft.traded_with_villager	35	None
minecraft.eat_cake_slice	36	None
minecraft.fill_cauldron	37	None
minecraft.use_cauldron	38	None
minecraft.clean_armor	39	None
minecraft.clean_banner	40	None
minecraft.clean_shulker_box	41	None
minecraft.interact_with_brewingstand	42	None
minecraft.interact_with_beacon	43	None
minecraft.inspect_dropper	44	None
minecraft.inspect_hopper	45	None
minecraft.inspect_dispenser	46	None
minecraft.play_noteblock	47	None
minecraft.tune_noteblock	48	None
minecraft.pot_flower	49	None
minecraft.trigger_trapped_chest	50	None
minecraft.open_enderchest	51	None
minecraft.enchant_item	52	None
minecraft.play_record	53	None
minecraft.interact_with_furnace	54	None
minecraft.interact_with_crafting_table	55	None
minecraft.open_chest	56	None
minecraft.sleep_in_bed	57	None
minecraft.open_shulker_box	58	None
minecraft.open_barrel	59	None
minecraft.interact_with_blast_furnace	60	None
minecraft.interact_with_smoker	61	None
minecraft.interact_with_lectern	62	None
minecraft.interact_with_campfire	63	None
minecraft.interact_with_cartography_table	64	None
minecraft.interact_with_loom	65	None
minecraft.interact_with_stonecutter	66	None
minecraft.bell_ring	67	None
minecraft.raid_trigger	68	None
minecraft.raid_win	69	None
minecraft.interact_with_anvil	70	None
minecraft.interact_with_grindstone	71	None
minecraft.target_hit	72	None
minecraft.interact_with_smithing_table	73	None

Units:

• None: just a normal number (formatted with 0 decimal places)
• Damage: value is 10 times the normal amount
• Distance: a distance in centimeters (hundredths of blocks)
• Time: a time span in ticks

Acknowledge Block Change

Acknowledges a user-initiated block change. After receiving this packet, the client will display the block state sent by the server instead of the one predicted by the client.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x05	Play	Client	Sequence ID	VarInt	Represents the sequence to acknowledge, this is used for properly syncing block changes to the client after interactions.

Set Block Destroy Stage

0–9 are the displayable destroy stages and each other number means that there is no animation on this coordinate.

Block break animations can still be applied on air; the animation will remain visible although there is no block being broken. However, if this is applied to a transparent block, odd graphical effects may happen, including water losing its transparency. (An effect similar to this can be seen in normal gameplay when breaking ice blocks)

If you need to display several break animations at the same time you have to give each of them a unique Entity ID. The entity ID does not need to correspond to an actual entity on the client. It is valid to use a randomly generated number.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x06	Play	Client	Entity ID	VarInt	The ID of the entity breaking the block.
			Location	Position	Block Position.
			Destroy Stage	Byte	0–9 to set it, any other value to remove it.

Block Entity Data

Sets the block entity associated with the block at the given location.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x07	Play	Client	Location	Position
			Type	VarInt	The type of the block entity
			NBT Data	NBT Tag	Data to set. May be a TAG_END (0), in which case the block entity at the given location is removed (though this is not required since the client will remove the block entity automatically on chunk unload or block removal).

Block Action

This packet is used for a number of actions and animations performed by blocks, usually non-persistent. The client ignores the provided block type and instead uses the block state in their world.

See Block Actions for a list of values.

This packet uses a block ID, not a block state.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x08	Play	Client	Location	Position	Block coordinates.
			Action ID (Byte 1)	Unsigned Byte	Varies depending on block — see Block Actions.
			Action Parameter (Byte 2)	Unsigned Byte	Varies depending on block — see Block Actions.
			Block Type	VarInt	The block type ID for the block. This must match the block at the given coordinates.

Block Update

Fired whenever a block is changed within the render distance.

Changing a block in a chunk that is not loaded is not a stable action. The Notchian client currently uses a shared empty chunk which is modified for all block changes in unloaded chunks; while in 1.9 this chunk never renders in older versions the changed block will appear in all copies of the empty chunk. Servers should avoid sending block changes in unloaded chunks and clients should ignore such packets.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x09	Play	Client	Location	Position	Block Coordinates.
			Block ID	VarInt	The new block state ID for the block as given in the global palette. See that section for more information.

Boss Bar

Packet ID	State	Bound To	Field Name		Field Type	Notes
0x0A	Play	Client	UUID		UUID	Unique ID for this bar.
			Action		VarInt Enum	Determines the layout of the remaining packet.
			Action	Field Name
			0: add	Title	Chat
				Health	Float	From 0 to 1. Values greater than 1 do not crash a Notchian client, and start rendering part of a second health bar at around 1.5.
				Color	VarInt Enum	Color ID (see below).
				Division	VarInt Enum	Type of division (see below).
				Flags	Unsigned Byte	Bit mask. 0x1: should darken sky, 0x2: is dragon bar (used to play end music), 0x04: create fog (previously was also controlled by 0x02).
			1: remove	no fields	no fields	Removes this boss bar.
			2: update health	Health	Float	as above
			3: update title	Title	Chat
			4: update style	Color	VarInt Enum	Color ID (see below).
				Dividers	VarInt Enum	as above
			5: update flags	Flags	Unsigned Byte	as above

ID	Color
0	Pink
1	Blue
2	Red
3	Green
4	Yellow
5	Purple
6	White

ID	Type of division
0	No division
1	6 notches
2	10 notches
3	12 notches
4	20 notches

Change Difficulty

Changes the difficulty setting in the client's option menu

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x0B	Play	Client	Difficulty	Unsigned Byte	0: peaceful, 1: easy, 2: normal, 3: hard.
			Difficulty locked?	Boolean

Clear Titles

Clear the client's current title information, with the option to also reset it.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x0C	Play	Client	Reset	Boolean

Command Suggestions Response

The server responds with a list of auto-completions of the last word sent to it. In the case of regular chat, this is a player username. Command names and parameters are also supported. The client sorts these alphabetically before listing them.

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x0D	Play	Client
			ID		VarInt		Transaction ID.
			Start		VarInt		Start of the text to replace.
			Length		VarInt		Length of the text to replace.
			Count		VarInt		Number of elements in the following array.
			Matches	Match	Array	String (32767)	One eligible value to insert, note that each command is sent separately instead of in a single string, hence the need for Count. Note that for instance this doesn't include a leading / on commands.
				Has tooltip		Boolean	True if the following is present.
				Tooltip		Optional Chat	Tooltip to display; only present if previous boolean is true.

Commands

Lists all of the commands on the server, and how they are parsed.

This is a directed graph, with one root node. Each redirect or child node must refer only to nodes that have already been declared.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x0E	Play	Client	Count	VarInt	Number of elements in the following array.
			Nodes	Array of Node	An array of nodes.
			Root index	VarInt	Index of the root node in the previous array.

For more information on this packet, see the Command Data article.

Close Container (clientbound)

This packet is sent from the server to the client when a window is forcibly closed, such as when a chest is destroyed while it's open. The notchian client disregards the provided window ID and closes any active window.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x0F	Play	Client	Window ID	Unsigned Byte	This is the ID of the window that was closed. 0 for inventory.

Set Container Content

The inventory slots

Sent by the server when items in multiple slots (in a window) are added/removed. This includes the main inventory, equipped armour and crafting slots. This packet with Window ID set to "0" is sent during the player joining sequence to initialise the player's inventory.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x10	Play	Client	Window ID	Unsigned Byte	The ID of window which items are being sent for. 0 for player inventory.
			State ID	VarInt	The last received State ID from either a Set Container Slot or a Set Container Content packet
			Count	VarInt	Number of elements in the following array.
			Slot Data	Array of Slot
			Carried Item	Slot	Item held by player.

See inventory windows for further information about how slots are indexed.

Set Container Property

This packet is used to inform the client that part of a GUI window should be updated.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x11	Play	Client	Window ID	Unsigned Byte
			Property	Short	The property to be updated, see below.
			Value	Short	The new value for the property, see below.

The meaning of the Property field depends on the type of the window. The following table shows the known combinations of window type and property, and how the value is to be interpreted.

Window type	Property	Value
Furnace	0: Fire icon (fuel left)	counting from fuel burn time down to 0 (in-game ticks)
	1: Maximum fuel burn time	fuel burn time or 0 (in-game ticks)
	2: Progress arrow	counting from 0 to maximum progress (in-game ticks)
	3: Maximum progress	always 200 on the notchian server
Enchantment Table	0: Level requirement for top enchantment slot	The enchantment's xp level requirement
	1: Level requirement for middle enchantment slot
	2: Level requirement for bottom enchantment slot
	3: The enchantment seed	Used for drawing the enchantment names (in SGA) clientside. The same seed is used to calculate enchantments, but some of the data isn't sent to the client to prevent easily guessing the entire list (the seed value here is the regular seed bitwise and 0xFFFFFFF0).
	4: Enchantment ID shown on mouse hover over top enchantment slot	The enchantment id (set to -1 to hide it), see below for values
	5: Enchantment ID shown on mouse hover over middle enchantment slot
	6: Enchantment ID shown on mouse hover over bottom enchantment slot
	7: Enchantment level shown on mouse hover over the top slot	The enchantment level (1 = I, 2 = II, 6 = VI, etc.), or -1 if no enchant
	8: Enchantment level shown on mouse hover over the middle slot
	9: Enchantment level shown on mouse hover over the bottom slot
Beacon	0: Power level	0-4, controls what effect buttons are enabled
	1: First potion effect	Potion effect ID for the first effect, or -1 if no effect
	2: Second potion effect	Potion effect ID for the second effect, or -1 if no effect
Anvil	0: Repair cost	The repair's cost in xp levels
Brewing Stand	0: Brew time	0 – 400, with 400 making the arrow empty, and 0 making the arrow full
	1: Fuel time	0 - 20, with 0 making the arrow empty, and 20 making the arrow full
Stonecutter	0: Selected recipe	The index of the selected recipe. -1 means none is selected.
Loom	0: Selected pattern	The index of the selected pattern. 0 means none is selected, 0 is also the internal id of the "base" pattern.
Lectern	0: Page number	The current page number, starting from 0.

For an enchanting table, the following numerical IDs are used:

Numerical ID	Enchantment ID	Enchantment Name
0	minecraft:protection	Protection
1	minecraft:fire_protection	Fire Protection
2	minecraft:feather_falling	Feather Falling
3	minecraft:blast_protection	Blast Protection
4	minecraft:projectile_protection	Projectile Protection
5	minecraft:respiration	Respiration
6	minecraft:aqua_affinity	Aqua Affinity
7	minecraft:thorns	Thorns
8	minecraft:depth_strider	Depth Strider
9	minecraft:frost_walker	Frost Walker
10	minecraft:binding_curse	Curse of Binding
11	minecraft:soul_speed	Soul Speed
12	minecraft:sharpness	Sharpness
13	minecraft:smite	Smite
14	minecraft:bane_of_arthropods	Bane of Arthropods
15	minecraft:knockback	Knockback
16	minecraft:fire_aspect	Fire Aspect
17	minecraft:looting	Looting
18	minecraft:sweeping	Sweeping Edge
19	minecraft:efficiency	Efficiency
20	minecraft:silk_touch	Silk Touch
21	minecraft:unbreaking	Unbreaking
22	minecraft:fortune	Fortune
23	minecraft:power	Power
24	minecraft:punch	Punch
25	minecraft:flame	Flame
26	minecraft:infinity	Infinity
27	minecraft:luck_of_the_sea	Luck of the Sea
28	minecraft:lure	Lure
29	minecraft:loyalty	Loyalty
30	minecraft:impaling	Impaling
31	minecraft:riptide	Riptide
32	minecraft:channeling	Channeling
33	minecraft:multishot	Multishot
34	minecraft:quick_charge	Quick Charge
35	minecraft:piercing	Piercing
36	minecraft:mending	Mending
37	minecraft:vanishing_curse	Curse of Vanishing

Set Container Slot

Sent by the server when an item in a slot (in a window) is added/removed.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x12	Play	Client	Window ID	Byte	The window which is being updated. 0 for player inventory. Note that all known window types include the player inventory. This packet will only be sent for the currently opened window while the player is performing actions, even if it affects the player inventory. After the window is closed, a number of these packets are sent to update the player's inventory window (0).
			State ID	VarInt	The last received State ID from either a Set Container Slot or a Set Container Content packet
			Slot	Short	The slot that should be updated.
			Slot Data	Slot

To set the cursor (the item currently dragged with the mouse), use -1 as Window ID and as Slot.

This packet can only be used to edit the hotbar of the player's inventory if window ID is set to 0 (slots 36 through 45) if the player is in creative, with their inventory open, and not in their survival inventory tab. Otherwise, when window ID is 0, it can edit any slot in the player's inventory. If the window ID is set to -2, then any slot in the inventory can be used but no add item animation will be played.

Set Cooldown

Applies a cooldown period to all items with the given type. Used by the Notchian server with enderpearls. This packet should be sent when the cooldown starts and also when the cooldown ends (to compensate for lag), although the client will end the cooldown automatically. Can be applied to any item, note that interactions still get sent to the server with the item but the client does not play the animation nor attempt to predict results (i.e block placing).

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x14	Play	Client	Item ID	VarInt	Numeric ID of the item to apply a cooldown to.
			Cooldown Ticks	VarInt	Number of ticks to apply a cooldown for, or 0 to clear the cooldown.

Chat Suggestions

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x15	Play	Client	Action	VarInt Enum	0: Add, 1: Remove, 2: Set
			Count	VarInt	Number of elements in the following array.
			Entries	Array of String

Plugin Message (clientbound)

Main article: Plugin channels

Mods and plugins can use this to send their data. Minecraft itself uses several plugin channels. These internal channels are in the minecraft namespace.

More information on how it works on Dinnerbone's blog. More documentation about internal and popular registered channels are here.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x16	Play	Client	Channel	Identifier	Name of the plugin channel used to send the data.
			Data	Byte Array (1048576)	Any data. The length of this array must be inferred from the packet length.

In Notchian client, the maximum data length is 1048576 bytes.

Hide Message

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x18	Play	Client	Signature Length	VarInt	Length of Signature.
			Signature	Byte Array	Bytes of the signature.

Disconnect (play)

Sent by the server before it disconnects a client. The client assumes that the server has already closed the connection by the time the packet arrives.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x19	Play	Client	Reason	Chat	Displayed to the client when the connection terminates.

Profileless Chat Message

Not much is known about this packet at the given moment. This needs to be updated

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x00	Play	Client	Message	Chat
			Message Type	VarInt
Message Name	Chat
Has Target Name	Boolean	True is the following is present.
Target Name	Chat	Only present if previous boolean is true.

Entity Event

Entity statuses generally trigger an animation for an entity. The available statuses vary by the entity's type (and are available to subclasses of that type as well).

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x1A	Play	Client	Entity ID	Int
			Entity Status	Byte Enum	See Entity statuses for a list of which statuses are valid for each type of entity.

Explosion

Sent when an explosion occurs (creepers, TNT, and ghast fireballs).

Each block in Records is set to air. Coordinates for each axis in record is int(X) + record.x

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x1B	Play	Client	X	Double
			Y	Double
			Z	Double
			Strength	Float	A strength greater than or equal to 2.0 spawns a minecraft:explosion_emitter particle, while a lesser strength spawns a minecraft:explosion particle.
			Record Count	VarInt	Number of elements in the following array.
			Records	Array of (Byte, Byte, Byte)	Each record is 3 signed bytes long; the 3 bytes are the XYZ (respectively) signed offsets of affected blocks.
			Player Motion X	Float	X velocity of the player being pushed by the explosion.
			Player Motion Y	Float	Y velocity of the player being pushed by the explosion.
			Player Motion Z	Float	Z velocity of the player being pushed by the explosion.

Unload Chunk

Tells the client to unload a chunk column.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x1C	Play	Client	Chunk X	Int	Block coordinate divided by 16, rounded down.
			Chunk Z	Int	Block coordinate divided by 16, rounded down.

It is legal to send this packet even if the given chunk is not currently loaded.

Game Event

Used for a wide variety of game events, from weather to bed use to gamemode to demo messages.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x1D	Play	Client	Event	Unsigned Byte	See below.
			Value	Float	Depends on Reason.

Events:

Event	Effect	Value
0	No respawn block available	Note: Sends message 'block.minecraft.spawn.not_valid'(You have no home bed or charged respawn anchor, or it was obstructed) to the client.
1	End raining
2	Begin raining
3	Change gamemode	0: Survival, 1: Creative, 2: Adventure, 3: Spectator.
4	Win game	0: Just respawn player. 1: Roll the credits and respawn player. Note that 1 is only sent by notchian server when player has not yet achieved advancement "The end?", else 0 is sent.
5	Demo event	0: Show welcome to demo screen 101: Tell movement controls 102: Tell jump control 103: Tell inventory control 104: Tell that the demo is over and print a message about how to take a screenshot.
6	Arrow hit player	Note: Sent when any player is struck by an arrow.
7	Rain level change	Note: Seems to change both skycolor and lightning. Rain level starting from 0 to 1.
8	Thunder level change	Note: Seems to change both skycolor and lightning (same as Rain level change, but doesn't start rain). It also requires rain to render by notchian client. Thunder level starting from 0 to 1.
9	Play pufferfish sting sound.
10	Play elder guardian mob appearance (effect and sound).
11	Enable respawn screen	0: Enable respawn screen, 1: Immediately respawn (sent when the doImmediateRespawn gamerule changes).

Open Horse Screen

This packet is used exclusively for opening the horse GUI. Open Screen is used for all other GUIs. The client will not open the inventory if the Entity ID does not point to an horse-like animal.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x1E	Play	Client	Window ID	Unsigned Byte
			Slot count	VarInt
			Entity ID	Integer

Initialize World Border

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x1F	Play	Client	X	Double
			Z	Double
			Old Diameter	Double	Current length of a single side of the world border, in meters.
			New Diameter	Double	Target length of a single side of the world border, in meters.
			Speed	VarLong	Number of real-time milliseconds until New Diameter is reached. It appears that Notchian server does not sync world border speed to game ticks, so it gets out of sync with server lag. If the world border is not moving, this is set to 0.
			Portal Teleport Boundary	VarInt	Resulting coordinates from a portal teleport are limited to ±value. Usually 29999984.
			Warning Blocks	VarInt	In meters.
			Warning Time	VarInt	In seconds as set by /worldborder warning time.

The Notchian client determines how solid to display the warning by comparing to whichever is higher, the warning distance or whichever is lower, the distance from the current diameter to the target diameter or the place the border will be after warningTime seconds. In pseudocode:

distance = max(min(resizeSpeed * 1000 * warningTime, abs(targetDiameter - currentDiameter)), warningDistance);
if (playerDistance < distance) {
    warning = 1.0 - playerDistance / distance;
} else {
    warning = 0.0;
}

Keep Alive (clientbound)

The server will frequently send out a keep-alive, each containing a random ID. The client must respond with the same payload (see serverbound Keep Alive). If the client does not respond to them for over 30 seconds, the server kicks the client. Vice versa, if the server does not send any keep-alives for 20 seconds, the client will disconnect and yields a "Timed out" exception.

The Notchian server uses a system-dependent time in milliseconds to generate the keep alive ID value.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x20	Play	Client	Keep Alive ID	Long

Chunk Data and Update Light

Main article: Chunk Format

See also: #Unload Chunk

	The following information needs to be added to this page:
	How do biomes work now? The biome change happened at the same time as the seed change, but it's not clear how/if biomes could be computed given that it's not the actual seed... (/r/mojira discussion which notes that it seems to be some kind of interpolation, and 3D biomes are only used in the nether)

This packet sends all block entities in the chunk (though sending them is not required; it is still legal to send them with Block Entity Data later). The light data in this packet is the same format as in the Update Light packet.

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x21	Play	Client	Chunk X		Int		Chunk coordinate (block coordinate divided by 16, rounded down)
			Chunk Z		Int		Chunk coordinate (block coordinate divided by 16, rounded down)
			Heightmaps		NBT		Compound containing one long array named MOTION_BLOCKING, which is a heightmap for the highest solid block at each position in the chunk (as a compacted long array with 256 entries, with the number of bits per entry varying depending on the world's height, defined by the formula ceil(log2(height + 1))). The Notchian server also adds a WORLD_SURFACE long array, the purpose of which is unknown, but it's not required for the chunk to be accepted.
			Size		VarInt		Size of Data in bytes
			Data		Byte array		See data structure in Chunk Format
			Number of block entities		VarInt		Number of elements in the following array
			Block Entity	Packed XZ	Array	Byte	The packed section coordinates, calculated from ((blockX & 15) << 4) | (blockZ & 15)
				Y		Short	The height relative to the world
				Type		VarInt	The type of block entity
				Data		NBT	The block entity's data, without the X, Y, and Z values
			Trust Edges		Boolean		If edges should be trusted for light updates.
			Sky Light Mask		BitSet		BitSet containing bits for each section in the world + 2. Each set bit indicates that the corresponding 16×16×16 chunk section has data in the Sky Light array below. The least significant bit is for blocks 16 blocks to 1 block below the min world height (one section below the world), while the most significant bit covers blocks 1 to 16 blocks above the max world height (one section above the world).
			Block Light Mask		BitSet		BitSet containing bits for each section in the world + 2. Each set bit indicates that the corresponding 16×16×16 chunk section has data in the Block Light array below. The order of bits is the same as in Sky Light Mask.
			Empty Sky Light Mask		BitSet		BitSet containing bits for each section in the world + 2. Each set bit indicates that the corresponding 16×16×16 chunk section has all zeros for its Sky Light data. The order of bits is the same as in Sky Light Mask.
			Empty Block Light Mask		BitSet		BitSet containing bits for each section in the world + 2. Each set bit indicates that the corresponding 16×16×16 chunk section has all zeros for its Block Light data. The order of bits is the same as in Sky Light Mask.
			Sky Light array count		VarInt		Number of entries in the following array; should match the number of bits set in Sky Light Mask
			Sky Light arrays	Length	Array	VarInt	Length of the following array in bytes (always 2048)
				Sky Light array		Array of 2048 bytes	There is 1 array for each bit set to true in the sky light mask, starting with the lowest value. Half a byte per light value. Indexed ((y<<8) | (z<<4) | x) / 2 If there's a remainder, masked 0xF0 else 0x0F.
			Block Light array count		VarInt		Number of entries in the following array; should match the number of bits set in Block Light Mask
			Block Light arrays	Length	Array	VarInt	Length of the following array in bytes (always 2048)
				Block Light array		Array of 2048 bytes	There is 1 array for each bit set to true in the block light mask, starting with the lowest value. Half a byte per light value. Indexed ((y<<8) | (z<<4) | x) / 2 If there's a remainder, masked 0xF0 else 0x0F.

Note that the Notchian client requires an Set Center Chunk packet when it crosses a chunk border, otherwise it'll only display render distance + 2 chunks around the chunk it spawned in.

The compacted array format has been adjusted so that individual entries no longer span across multiple longs, affecting the main data array and heightmaps.

New format, 5 bits per block, containing the following references to blocks in a palette (not shown): 122344566480743131516914101202

0020863148418841 0000000000100000100001100011000101001000010000011000100001000001
01018A7260F68C87 0000000100000001100010100111001001100000111101101000110010000111

World Event

Sent when a client is to play a sound or particle effect.

By default, the Minecraft client adjusts the volume of sound effects based on distance. The final boolean field is used to disable this, and instead the effect is played from 2 blocks away in the correct direction. Currently this is only used for effect 1023 (wither spawn), effect 1028 (enderdragon death), and effect 1038 (end portal opening); it is ignored on other effects.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x22	Play	Client	Event	Int	The event, see below.
			Location	Position	The location of the event.
			Data	Int	Extra data for certain events, see below.
			Disable Relative Volume	Boolean	See above.

Events:

ID	Name	Data
Sound
1000	Dispenser dispenses
1001	Dispenser fails to dispense
1002	Dispenser shoots
1003	Ender eye launched
1004	Firework shot
1005	Iron door opened
1006	Wooden door opened
1007	Wooden trapdoor opened
1008	Fence gate opened
1009	Fire extinguished
1010	Play record	Special case, see below for more info.
1011	Iron door closed
1012	Wooden door closed
1013	Wooden trapdoor closed
1014	Fence gate closed
1015	Ghast warns
1016	Ghast shoots
1017	Enderdragon shoots
1018	Blaze shoots
1019	Zombie attacks wood door
1020	Zombie attacks iron door
1021	Zombie breaks wood door
1022	Wither breaks block
1023	Wither spawned
1024	Wither shoots
1025	Bat takes off
1026	Zombie infects
1027	Zombie villager converted
1028	Ender dragon death
1029	Anvil destroyed
1030	Anvil used
1031	Anvil landed
1032	Portal travel
1033	Chorus flower grown
1034	Chorus flower died
1035	Brewing stand brewed
1036	Iron trapdoor opened
1037	Iron trapdoor closed
1038	End portal created in overworld
1039	Phantom bites
1040	Zombie converts to drowned
1041	Husk converts to zombie by drowning
1042	Grindstone used
1043	Book page turned
Particle
1500	Composter composts
1501	Lava converts block (either water to stone, or removes existing blocks such as torches)
1502	Redstone torch burns out
1503	Ender eye placed
2000	Spawns 10 smoke particles, e.g. from a fire	Direction, see below.
2001	Block break + block break sound	Block state, as an index into the global palette.
2002	Splash potion. Particle effect + glass break sound.	RGB color as an integer (e.g. 8364543 for #7FA1FF).
2003	Eye of Ender entity break animation — particles and sound
2004	Mob spawn particle effect: smoke + flames
2005	Bonemeal particles	How many particles to spawn (if set to 0, 15 are spawned).
2006	Dragon breath
2007	Instant splash potion. Particle effect + glass break sound.	RGB color as an integer (e.g. 8364543 for #7FA1FF).
2008	Ender dragon destroys block
2009	Wet sponge vaporizes in nether
3000	End gateway spawn
3001	Enderdragon growl
3002	Electric spark
3003	Copper apply wax
3004	Copper remove wax
3005	Copper scrape oxidation

Smoke directions:

ID	Direction
0	Down
1	Up
2	North
3	South
4	West
5	East

Play record: This is actually a special case within this packet. You can start/stop a record at a specific location. Use a valid Record ID to start a record (or overwrite a currently playing one), any other value will stop the record. See Data Generators for information on item IDs.

Particle

Displays the named particle

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x23	Play	Client	Particle ID	VarInt	The particle ID listed in the particle data type.
			Long Distance	Boolean	If true, particle distance increases from 256 to 65536.
			X	Double	X position of the particle.
			Y	Double	Y position of the particle.
			Z	Double	Z position of the particle.
			Offset X	Float	This is added to the X position after being multiplied by random.nextGaussian().
			Offset Y	Float	This is added to the Y position after being multiplied by random.nextGaussian().
			Offset Z	Float	This is added to the Z position after being multiplied by random.nextGaussian().
			Max Speed	Float
			Particle Count	Int	The number of particles to create.
			Data	Varies	The variable data listed in the particle data type.

Update Light

Updates light levels for a chunk. See Light for information on how lighting works in Minecraft.

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x24	Play	Client	Chunk X		VarInt		Chunk coordinate (block coordinate divided by 16, rounded down)
			Chunk Z		VarInt		Chunk coordinate (block coordinate divided by 16, rounded down)
			Trust Edges		Boolean		If edges should be trusted for light updates.
			Sky Light Mask		BitSet		BitSet containing bits for each section in the world + 2. Each set bit indicates that the corresponding 16×16×16 chunk section has data in the Sky Light array below. The least significant bit is for blocks 16 blocks to 1 block below the min world height (one section below the world), while the most significant bit covers blocks 1 to 16 blocks above the max world height (one section above the world).
			Block Light Mask		BitSet		BitSet containing bits for each section in the world + 2. Each set bit indicates that the corresponding 16×16×16 chunk section has data in the Block Light array below. The order of bits is the same as in Sky Light Mask.
			Empty Sky Light Mask		BitSet		BitSet containing bits for each section in the world + 2. Each set bit indicates that the corresponding 16×16×16 chunk section has all zeros for its Sky Light data. The order of bits is the same as in Sky Light Mask.
			Empty Block Light Mask		BitSet		BitSet containing bits for each section in the world + 2. Each set bit indicates that the corresponding 16×16×16 chunk section has all zeros for its Block Light data. The order of bits is the same as in Sky Light Mask.
			Sky Light array count		VarInt		Number of entries in the following array; should match the number of bits set in Sky Light Mask
			Sky Light arrays	Length	Array	VarInt	Length of the following array in bytes (always 2048)
				Sky Light array		Array of 2048 bytes	There is 1 array for each bit set to true in the sky light mask, starting with the lowest value. Half a byte per light value.
			Block Light array count		VarInt		Number of entries in the following array; should match the number of bits set in Block Light Mask
			Block Light arrays	Length	Array	VarInt	Length of the following array in bytes (always 2048)
				Block Light array		Array of 2048 bytes	There is 1 array for each bit set to true in the block light mask, starting with the lowest value. Half a byte per light value.

A bit will never be set in both the block light mask and the empty block light mask, though it may be present in neither of them (if the block light does not need to be updated for the corresponding chunk section). The same applies to the sky light mask and the empty sky light mask.

Login (play)

See Protocol Encryption for information on logging in.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x25	Play	Client	Entity ID	Int	The player's Entity ID (EID).
			Is hardcore	Boolean
			Gamemode	Unsigned Byte	0: Survival, 1: Creative, 2: Adventure, 3: Spectator.
			Previous Gamemode	Byte	0: survival, 1: creative, 2: adventure, 3: spectator. The hardcore flag is not included. The previous gamemode. Defaults to -1 if there is no previous gamemode. (More information needed)
			Dimension Count	VarInt	Size of the following array.
			Dimension Names	Array of Identifier	Identifiers for all dimensions on the server.
			Registry Codec	NBT Tag Compound	Represents certain registries that are sent from the server and are applied on the client.
			Dimension Type	Identifier	Name of the dimension type being spawned into.
			Dimension Name	Identifier	Name of the dimension being spawned into.
			Hashed seed	Long	First 8 bytes of the SHA-256 hash of the world's seed. Used client side for biome noise
			Max Players	VarInt	Was once used by the client to draw the player list, but now is ignored.
			View Distance	VarInt	Render distance (2-32).
			Simulation Distance	VarInt	The distance that the client will process specific things, such as entities.
			Reduced Debug Info	Boolean	If true, a Notchian client shows reduced information on the debug screen. For servers in development, this should almost always be false.
			Enable respawn screen	Boolean	Set to false when the doImmediateRespawn gamerule is true.
			Is Debug	Boolean	True if the world is a debug mode world; debug mode worlds cannot be modified and have predefined blocks.
			Is Flat	Boolean	True if the world is a superflat world; flat worlds have different void fog and a horizon at y=0 instead of y=63.
			Has death location	Boolean	If true, then the next two fields are present.
			Death dimension name	Identifier	Name of the dimension the player died in.
			Death location	Position	The location that the player died at.

The Registry Codec NBT Tag Compound (Default value in JSON as of 1.19, 1.19.2) includes three registries: "minecraft:dimension_type", "minecraft:worldgen/biome", and "minecraft:chat_type".

Name	Type	Notes
minecraft:dimension_type	TAG_Compound	The dimension type registry (see below).
minecraft:worldgen/biome	TAG_Compound	The biome registry (see below).
minecraft:chat_type	TAG_Compound	The chat type registry (see below).

Dimension type registry:

Name	Type	Notes
type	TAG_String	The name of the registry. Always "minecraft:dimension_type".
value	TAG_List	List of dimension types registry entries (see below).

Dimension type registry entry:

Name	Type	Notes
name	TAG_String	The name of the dimension type (for example, "minecraft:overworld").
id	TAG_Int	The protocol ID of the dimension (matches the index of the element in the registry list).
element	TAG_Compound	The dimension type (see below).

Dimension type:

Name	Type	Meaning		Values
piglin_safe	TAG_Byte	Whether piglins shake and transform to zombified piglins.		1: true, 0: false.
has_raids	TAG_Byte	Whether players with the Bad Omen effect can cause a raid.		1: true, 0: false.
monster_spawn_light_level	TAG_Int or TAG_Compound	Possibly the light level(s) at which monsters can spawn.	When TAG_Int, 0 - 15. When TAG_Compound, contains the fields: type (TAG_String), appears to be always "minecraft:uniform", and value (TAG_Compound), which contains the fields: max_inclusive (TAG_Int), min_inclusive (TAG_Int).
monster_spawn_block_light_limit	TAG_Int
natural	TAG_Byte	When false, compasses spin randomly. When true, nether portals can spawn zombified piglins.		1: true, 0: false.
ambient_light	TAG_Float	How much light the dimension has.		0.0 to 1.0.
fixed_time	Optional TAG_Long	If set, the time of the day is the specified value.		If set, 0 to 24000.
infiniburn	TAG_String	A resource location defining what block tag to use for infiniburn.		"#" or minecraft resource "#minecraft:...".
respawn_anchor_works	TAG_Byte	Whether players can charge and use respawn anchors.		1: true, 0: false.
has_skylight	TAG_Byte	Whether the dimension has skylight access or not.		1: true, 0: false.
bed_works	TAG_Byte	Whether players can use a bed to sleep.		1: true, 0: false.
effects	TAG_String	?		"minecraft:overworld", "minecraft:the_nether", "minecraft:the_end" or something else.
min_y	TAG_Int	The minimum Y level.		A multiple of 16. Example: -64
height	TAG_Int	The maximum height.		A multiple of 16. Example: 256
logical_height	TAG_Int	The maximum height to which chorus fruits and nether portals can bring players within this dimension.		0-384.
coordinate_scale	TAG_Double	The multiplier applied to coordinates when traveling to the dimension.		0.00001 - 30000000.0
ultrawarm	TAG_Byte	Whether the dimensions behaves like the nether (water evaporates and sponges dry) or not. Also causes lava to spread thinner.		1: true, 0: false.
has_ceiling	TAG_Byte	Whether the dimension has a bedrock ceiling or not. When true, causes lava to spread faster.		1: true, 0: false.

Biome registry:

Name	Type	Notes
type	TAG_String	The name of the registry. Always "minecraft:worldgen/biome".
value	TAG_List	List of biome registry entries (see below).

Biome registry entry:

Name	Type	Notes
name	TAG_String	The name of the biome (for example, "minecraft:ocean").
id	TAG_Int	The protocol ID of the biome (matches the index of the element in the registry list).
element	TAG_Compound	The biome properties (see below).

Biome properties:

Name			Type		Meaning		Values
precipitation			TAG_String		The type of precipitation in the biome.		"rain", "snow", or "none".
depth			Optional TAG_Float		The depth factor of the biome.		The default values vary between 1.5 and -1.8.
temperature			TAG_Float		The temperature factor of the biome.		The default values vary between 2.0 and -0.5.
scale			Optional TAG_Float		?		The default values vary between 1.225 and 0.0.
downfall			TAG_Float		?		The default values vary between 1.0 and 0.0.
category			Optional TAG_String		The category of the biome.		Known values are "ocean", "plains", "desert", "forest", "extreme_hills", "taiga", "swamp", "river", "nether", "the_end", "icy", "mushroom", "beach", "jungle", "mesa", "savanna", and "none".
temperature_modifier			Optional TAG_String		?		The only known value is "frozen".
effects	sky_color		TAG_Compound	TAG_Int	The color of the sky.		Example: 8364543, which is #7FA1FF in RGB.
	water_fog_color			TAG_Int	Possibly the tint color when swimming.		Example: 8364543, which is #7FA1FF in RGB.
	fog_color			TAG_Int	Possibly the color of the fog effect when looking past the view distance.		Example: 8364543, which is #7FA1FF in RGB.
	water_color			TAG_Int	The tint color of the water blocks.		Example: 8364543, which is #7FA1FF in RGB.
	foliage_color			Optional TAG_Int	The tint color of the grass.		Example: 8364543, which is #7FA1FF in RGB.
	grass_color			Optional TAG_Int	?		Example: 8364543, which is #7FA1FF in RGB.
	grass_color_modifier			Optional TAG_String	Unknown, likely affects foliage color.		If set, known values are "swamp" and "dark_forest".
	music			Optional TAG_Compound	Music properties for the biome.		If present, contains the fields: replace_current_music (TAG_Byte), sound (TAG_String), max_delay (TAG_Int), min_delay (TAG_Int).
	ambient_sound			Optional TAG_String	Ambient soundtrack.		If present, the ID of a soundtrack. Example: "minecraft:ambient.basalt_deltas.loop".
	additions_sound			Optional TAG_Compound	Additional ambient sound that plays randomly.		If present, contains the fields: sound (TAG_String), tick_chance (TAG_Double).
	mood_sound			Optional TAG_Compound	Additional ambient sound that plays at an interval.		If present, contains the fields: sound (TAG_String), tick_delay (TAG_Int), offset (TAG_Double), block_search_extent (TAG_Int).
	particle	probability	Optional TAG_Compound	TAG_FLOAT	Particles that appear randomly in the biome.	Possibly the probability of spawning the particle.	?
		options		TAG_COMPOUND		The properties of the particle to spawn.	Contains the field "type" (TAG_String), which identifies the particle type.

Chat registry:

Name	Type	Notes
type	TAG_String	The name of the registry. Always "minecraft:chat_type".
value	TAG_List	List of chat registry entries (see below).

Map Data

Updates a rectangular area on a map item.

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x26	Play	Client	Map ID		VarInt		Map ID of the map being modified
			Scale		Byte		From 0 for a fully zoomed-in map (1 block per pixel) to 4 for a fully zoomed-out map (16 blocks per pixel)
			Locked		Boolean		True if the map has been locked in a cartography table
			Tracking Position		Boolean		Specifies whether player and item frame icons are shown
			Icon Count		VarInt		Number of elements in the following array. Only present if "Tracking Position" is true.
			Icon	Type	Array	VarInt enum	See below
				X		Byte	Map coordinates: -128 for furthest left, +127 for furthest right
				Z		Byte	Map coordinates: -128 for highest, +127 for lowest
				Direction		Byte	0-15
				Has Display Name		Boolean
				Display Name		Optional Chat	Only present if previous Boolean is true
			Columns		Unsigned Byte		Number of columns updated
			Rows		Optional Unsigned Byte		Only if Columns is more than 0; number of rows updated
			X		Optional Byte		Only if Columns is more than 0; x offset of the westernmost column
			Z		Optional Byte		Only if Columns is more than 0; z offset of the northernmost row
			Length		Optional VarInt		Only if Columns is more than 0; length of the following array
			Data		Optional Array of Unsigned Byte		Only if Columns is more than 0; see Map item format

For icons, a direction of 0 is a vertical icon and increments by 22.5° (360/16).

Types are based off of rows and columns in map_icons.png:

Icon type	Result
0	White arrow (players)
1	Green arrow (item frames)
2	Red arrow
3	Blue arrow
4	White cross
5	Red pointer
6	White circle (off-map players)
7	Small white circle (far-off-map players)
8	Mansion
9	Temple
10	White Banner
11	Orange Banner
12	Magenta Banner
13	Light Blue Banner
14	Yellow Banner
15	Lime Banner
16	Pink Banner
17	Gray Banner
18	Light Gray Banner
19	Cyan Banner
20	Purple Banner
21	Blue Banner
22	Brown Banner
23	Green Banner
24	Red Banner
25	Black Banner
26	Treasure marker

Merchant Offers

The list of trades a villager NPC is offering.

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x27	Play	Client
			Window ID		VarInt		The ID of the window that is open; this is an int rather than a byte.
			Size		VarInt		The number of trades in the following array.
			Trades	Input item 1	Array	Slot	The first item the player has to supply for this villager trade. The count of the item stack is the default "price" of this trade.
				Output item		Slot	The item the player will receive from this villager trade.
				Input item 2		Slot	The second item the player has to supply for this villager trade; only present if has a second item is true.
				Trade disabled		Boolean	True if the trade is disabled; false if the trade is enabled.
				Number of trade uses		Integer	Number of times the trade has been used so far. If equal to the maximum number of trades, the client will display a red X.
				Maximum number of trade uses		Integer	Number of times this trade can be used before it's exhausted.
				XP		Integer	Amount of XP the villager will earn each time the trade is used.
				Special Price		Integer	Can be zero or negative. The number is added to the price when an item is discounted due to player reputation or other effects.
				Price Multiplier		Float	Can be low (0.05) or high (0.2). Determines how much demand, player reputation, and temporary effects will adjust the price.
				Demand		Integer	If positive, causes the price to increase. Negative values seem to be treated the same as zero.
				Villager level		VarInt		Appears on the trade GUI; meaning comes from the translation key merchant.level. + level. 1: Novice, 2: Apprentice, 3: Journeyman, 4: Expert, 5: Master.
			Experience		VarInt		Total experience for this villager (always 0 for the wandering trader).
			Is regular villager		Boolean		True if this is a regular villager; false for the wandering trader. When false, hides the villager level and some other GUI elements.
			Can restock		Boolean		True for regular villagers and false for the wandering trader. If true, the "Villagers restock up to two times per day." message is displayed when hovering over disabled trades.

Modifiers can increase or decrease the number of items for the first input slot. The second input slot and the output slot never change the nubmer of items. The number of items may never be less than 1, and never more than the stack size. If special price and demand are both zero, only the default price is displayed. If either is non-zero, then the adjusted price is displayed next to the crossed-out default price. The adjusted prices is calculated as follows:

Adjusted price = default price + floor(default price x multiplier x demand) + special price

The merchant UI, for reference

Update Entity Position

This packet is sent by the server when an entity moves less then 8 blocks; if an entity moves more than 8 blocks Teleport Entity should be sent instead.

This packet allows at most 8 blocks movement in any direction, because short range is from -32768 to 32767. And 32768 / (128 * 32) = 8.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x28	Play	Client	Entity ID	VarInt
			Delta X	Short	Change in X position as (currentX * 32 - prevX * 32) * 128.
			Delta Y	Short	Change in Y position as (currentY * 32 - prevY * 32) * 128.
			Delta Z	Short	Change in Z position as (currentZ * 32 - prevZ * 32) * 128.
			On Ground	Boolean

Update Entity Position and Rotation

This packet is sent by the server when an entity rotates and moves. Since a short range is limited from -32768 to 32767, and movement is offset of fixed-point numbers, this packet allows at most 8 blocks movement in any direction. (-32768 / (32 * 128) == -8)

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x29	Play	Client	Entity ID	VarInt
			Delta X	Short	Change in X position as (currentX * 32 - prevX * 32) * 128.
			Delta Y	Short	Change in Y position as (currentY * 32 - prevY * 32) * 128.
			Delta Z	Short	Change in Z position as (currentZ * 32 - prevZ * 32) * 128.
			Yaw	Angle	New angle, not a delta.
			Pitch	Angle	New angle, not a delta.
			On Ground	Boolean

Update Entity Rotation

This packet is sent by the server when an entity rotates.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x2A	Play	Client	Entity ID	VarInt
			Yaw	Angle	New angle, not a delta.
			Pitch	Angle	New angle, not a delta.
			On Ground	Boolean

Move Vehicle (clientbound)

Note that all fields use absolute positioning and do not allow for relative positioning.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x2B	Play	Client	X	Double	Absolute position (X coordinate).
			Y	Double	Absolute position (Y coordinate).
			Z	Double	Absolute position (Z coordinate).
			Yaw	Float	Absolute rotation on the vertical axis, in degrees.
			Pitch	Float	Absolute rotation on the horizontal axis, in degrees.

Open Book

Sent when a player right clicks with a signed book. This tells the client to open the book GUI.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x2C	Play	Client	Hand	VarInt enum	0: Main hand, 1: Off hand .

Open Screen

This is sent to the client when it should open an inventory, such as a chest, workbench, or furnace. This message is not sent anywhere for clients opening their own inventory. Resending this packet with already existing window id, will update the window title and window type without closing the window. For horses, use Open Horse Screen.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x2D	Play	Client	Window ID	VarInt	A unique id number for the window to be displayed. Notchian server implementation is a counter, starting at 1.
			Window Type	VarInt	The window type to use for display. Contained in the minecraft:menu registry; see Inventory for the different values.
			Window Title	Chat	The title of the window.

Open Sign Editor

Sent when the client has placed a sign and is allowed to send Update Sign. There must already be a sign at the given location (which the client does not do automatically) - send a Block Update first.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x2E	Play	Client	Location	Position

Ping (play)

Packet is not used by the Notchian server. When sent to the client, client responds with a Pong packet with the same id.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x2F	Play	Client	ID	Int

Place Ghost Recipe

Response to the serverbound packet (Place Recipe), with the same recipe ID. Appears to be used to notify the UI.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x30	Play	Client	Window ID	Byte
			Recipe	Identifier	A recipe ID.

Player Abilities (clientbound)

The latter 2 floats are used to indicate the field of view and flying speed respectively, while the first byte is used to determine the value of 4 booleans.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x31	Play	Client	Flags	Byte	Bit field, see below.
			Flying Speed	Float	0.05 by default.
			Field of View Modifier	Float	Modifies the field of view, like a speed potion. A Notchian server will use the same value as the movement speed sent in the Update Attributes packet, which defaults to 0.1 for players.

About the flags:

Field	Bit
Invulnerable	0x01
Flying	0x02
Allow Flying	0x04
Creative Mode (Instant Break)	0x08

Player Chat Message

Sends the client a message from a player.

Currently a lot is unknown about this packet, blank descriptions are for those that are unknown

Packet ID	State	Bound To	Sector	Field Name		Field Type	Notes
0x33	Play	Client	Header	Sender		UUID	Used by the Notchian client for the disableChat launch option. Setting both longs to 0 will always display the message regardless of the setting.
				Index		VarInt
				Message Signature Present		boolean	States if a message signature is present
				Message Signature bytes		Optional Byte Array	Only present if Message Signature Present is true. Cryptography, the signature consists of the Sender UUID, Timestamp and Original Chat Content. Modifying any of these values in the packet will cause this signature to fail. This buffer should(?) always be 256 bytes long.
			Body	Message		String
				Timestamp		long	Represents the time the message was signed as milliseconds since the epoch, used to check if the message was received within 2 minutes of it being sent.
				Salt		long	Cryptography, used for validating the message signature.
			Previous Messages	Total Previous Messages		VarInt
				Array	Message ID	VarInt	TODO: This genuinely might be length I really don't know.
					Signature	Optional Byte Array	The previous message's signature
			Other	Unsigned Content Present		boolean
				Unsigned Content		Optional Chat
				Filter Type		Enum VarInt	If the message has been filtered
				Filter Type Bits		Optional BitSet
			Network target	Chat Type		VarInt	The ChatType (sent in Login(Play)) used for this message
				Network name		Chat
				Network target name present		boolean
				Network target name		Optional Chat

Player Chat Handling Logic

Filter Types:

The filter type mask should NOT be specified unless partially filtered is selected

ID	Name	Description
0	PASS_THROUGH	No filters applied
1	FULLY_FILTERED	All filters applied
2	PARTIALLY_FILTERED	Only some filters are applied.

End Combat

Unused by the Notchain client. This data was once used for twitch.tv metadata circa 1.8.f

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x34	Play	Client	Duration	VarInt	Length of the combat in ticks.
			Entity ID	Int	ID of the primary opponent of the ended combat, or -1 if there is no obvious primary opponent.

Enter Combat

Unused by the Notchain client. This data was once used for twitch.tv metadata circa 1.8.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x35	Play	Client	no fields

Combat Death

Used to send a respawn screen.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x36	Play	Client	Player ID	VarInt	Entity ID of the player that died (should match the client's entity ID).
			Entity ID	Int	The killer entity's ID, or -1 if there is no obvious killer.
			Message	Chat	The death message.

Player Remove

Sent by the server when a player is leaves the game.

Packet ID	State	Bound To	Field Name				Field Type			Notes
0x00	Play	Client	Number of Players		VarInt
			Player	Player	UUID

Player Info

Sent by the server to update the user list (<tab> in the client).

Packet ID	State	Bound To	Field Name				Field Type			Notes
0x37	Play	Client	Action				VarInt			Determines the rest of the Player format after the UUID.
			Number Of Players				VarInt			Number of elements in the following array.
			Player	UUID			Array	UUID
				Action	Field Name
				0: add player	Name			String (16)
					Number Of Properties			VarInt		Number of elements in the following array.
					Property	Name		Array	String (32767)
						Value			String (32767)
						Is Signed			Boolean
						Signature			Optional String (32767)	Only if Is Signed is true.
					Gamemode			VarInt
					Ping			VarInt		Measured in milliseconds.
					Has Display Name			Boolean
					Display Name			Optional Chat		Only if Has Display Name is true.
					Has Sig Data			Boolean		Whether or not the next 5 fields should be sent.
					Timestamp			Long		When the key data will expire.
					Public Key Length			VarInt		Length of Public Key. Optional.
					Public Key			Byte Array		The encoded bytes of the public key the client received from Mojang.
					Signature Length			VarInt		Length of Signature.
					Signature			Byte Array		The bytes of the public key signature the client received from Mojang.
				1: update gamemode	Gamemode			VarInt
				2: update latency	Ping			VarInt		Measured in milliseconds.
				3: update display name	Has Display Name			Boolean
					Display Name			Optional Chat		Only send if Has Display Name is true.
				4: remove player	no fields			no fields

The Property field looks as in the response of Mojang API#UUID -> Profile + Skin/Cape, except of course using the protocol format instead of JSON. That is, each player will usually have one property with Name “textures” and Value being a base64-encoded JSON string as documented at Mojang API#UUID -> Profile + Skin/Cape. An empty properties array is also acceptable, and will cause clients to display the player with one of the two default skins depending on UUID.

Ping values correspond with icons in the following way:

• A ping that negative (i.e. not known to the server yet) will result in the no connection icon.
• A ping under 150 milliseconds will result in 5 bars
• A ping under 300 milliseconds will result in 4 bars
• A ping under 600 milliseconds will result in 3 bars
• A ping under 1000 milliseconds (1 second) will result in 2 bars
• A ping greater than or equal to 1 second will result in 1 bar.

Look At

Used to rotate the client player to face the given location or entity (for /teleport [<targets>] <x> <y> <z> facing).

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x38	Play	Client
			Feet/eyes	VarInt enum	Values are feet=0, eyes=1. If set to eyes, aims using the head position; otherwise aims using the feet position.
			Target x	Double	x coordinate of the point to face towards.
			Target y	Double	y coordinate of the point to face towards.
			Target z	Double	z coordinate of the point to face towards.
			Is entity	Boolean	If true, additional information about an entity is provided.
			Entity ID	Optional VarInt	Only if is entity is true — the entity to face towards.
			Entity feet/eyes	Optional VarInt enum	Whether to look at the entity's eyes or feet. Same values and meanings as before, just for the entity's head/feet.

If the entity given by entity ID cannot be found, this packet should be treated as if is entity was false.

Synchronize Player Position

Updates the player's position on the server. This packet will also close the “Downloading Terrain” screen when joining/respawning.

If the distance between the last known position of the player on the server and the new position set by this packet is greater than 100 meters, the client will be kicked for “You moved too quickly :( (Hacking?)”.

Also if the fixed-point number of X or Z is set greater than 3.2E7D the client will be kicked for “Illegal position”.

Yaw is measured in degrees, and does not follow classical trigonometry rules. The unit circle of yaw on the XZ-plane starts at (0, 1) and turns counterclockwise, with 90 at (-1, 0), 180 at (0, -1) and 270 at (1, 0). Additionally, yaw is not clamped to between 0 and 360 degrees; any number is valid, including negative numbers and numbers greater than 360.

Pitch is measured in degrees, where 0 is looking straight ahead, -90 is looking straight up, and 90 is looking straight down.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x39	Play	Client	X	Double	Absolute or relative position, depending on Flags.
			Y	Double	Absolute or relative position, depending on Flags.
			Z	Double	Absolute or relative position, depending on Flags.
			Yaw	Float	Absolute or relative rotation on the X axis, in degrees.
			Pitch	Float	Absolute or relative rotation on the Y axis, in degrees.
			Flags	Byte	Bit field, see below.
			Teleport ID	VarInt	Client should confirm this packet with Confirm Teleportation containing the same Teleport ID.
			Dismount Vehicle	Boolean	True if the player should dismount their vehicle.

About the Flags field:

<Dinnerbone> It's a bitfield, X/Y/Z/Y_ROT/X_ROT. If X is set, the x value is relative and not absolute.

Field	Bit
X	0x01
Y	0x02
Z	0x04
Y_ROT	0x08
X_ROT	0x10

Update Recipe Book

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x3A	Play	Client
			Action	VarInt	0: init, 1: add, 2: remove.
			Crafting Recipe Book Open	Boolean	If true, then the crafting recipe book will be open when the player opens its inventory.
			Crafting Recipe Book Filter Active	Boolean	If true, then the filtering option is active when the players opens its inventory.
			Smelting Recipe Book Open	Boolean	If true, then the smelting recipe book will be open when the player opens its inventory.
			Smelting Recipe Book Filter Active	Boolean	If true, then the filtering option is active when the players opens its inventory.
			Blast Furnace Recipe Book Open	Boolean	If true, then the blast furnace recipe book will be open when the player opens its inventory.
			Blast Furnace Recipe Book Filter Active	Boolean	If true, then the filtering option is active when the players opens its inventory.
			Smoker Recipe Book Open	Boolean	If true, then the smoker recipe book will be open when the player opens its inventory.
			Smoker Recipe Book Filter Active	Boolean	If true, then the filtering option is active when the players opens its inventory.
			Array size 1	VarInt	Number of elements in the following array.
			Recipe IDs	Array of Identifier
			Array size 2	Optional VarInt	Number of elements in the following array, only present if mode is 0 (init).
			Recipe IDs	Optional Array of Identifier	Only present if mode is 0 (init)

Action:

• 0 (init) = All the recipes in list 1 will be tagged as displayed, and all the recipes in list 2 will be added to the recipe book. Recipes that aren't tagged will be shown in the notification.
• 1 (add) = All the recipes in the list are added to the recipe book and their icons will be shown in the notification.
• 2 (remove) = Remove all the recipes in the list. This allows them to be re-displayed when they are re-added.

Remove Entities

Sent by the server when an entity is to be destroyed on the client.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x3B	Play	Client	Count	VarInt	Number of elements in the following array.
			Entity IDs	Array of VarInt	The list of entities to destroy.

Remove Entity Effect

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x3C	Play	Client	Entity ID	VarInt
			Effect ID	VarInt	See this table.

Resource Pack (clientbound)

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x3D	Play	Client	URL	String (32767)	The URL to the resource pack.
			Hash	String (40)	A 40 character hexadecimal and lowercase SHA-1 hash of the resource pack file. If it's not a 40 character hexadecimal string, the client will not use it for hash verification and likely waste bandwidth — but it will still treat it as a unique id
			Forced	Boolean	The notchian client will be forced to use the resource pack from the server. If they decline they will be kicked from the server.
			Has Prompt Message	Boolean	true If the next field will be sent false otherwise. When false, this is the end of the packet
			Prompt Message	Optional Chat	This is shown in the prompt making the client accept or decline the resource pack.

Respawn

To change the player's dimension (overworld/nether/end), send them a respawn packet with the appropriate dimension, followed by prechunks/chunks for the new dimension, and finally a position and look packet. You do not need to unload chunks, the client will do it automatically.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x3E	Play	Client	Dimension Type	Identifier	Valid dimensions are defined per dimension registry sent in Login (play)
			Dimension Name	Identifier	Name of the dimension being spawned into.
			Hashed seed	Long	First 8 bytes of the SHA-256 hash of the world's seed. Used client side for biome noise
			Gamemode	Unsigned Byte	0: survival, 1: creative, 2: adventure, 3: spectator. The hardcore flag is not included
			Previous Gamemode	Byte	-1: null 0: survival, 1: creative, 2: adventure, 3: spectator. The hardcore flag is not included. The previous gamemode. (More information needed)
			Is Debug	Boolean	True if the world is a debug mode world; debug mode worlds cannot be modified and have predefined blocks.
			Is Flat	Boolean	True if the world is a superflat world; flat worlds have different void fog and a horizon at y=0 instead of y=63.
			Copy metadata	Boolean	If false, metadata is reset on the respawned player entity. Set to true for dimension changes (including the dimension change triggered by sending client status perform respawn to exit the end poem/credits), and false for normal respawns.
			Has death location	Boolean	If true, then the next two fields are present.
			Death dimension Name	Identifier	Name of the dimension the player died in.
			Death location	Position	The location that the player died at.

Avoid changing player's dimension to same dimension they were already in unless they are dead. If you change the dimension to one they are already in, weird bugs can occur, such as the player being unable to attack other players in new world (until they die and respawn).

Before 1.16, if you must respawn a player in the same dimension without killing them, send two respawn packets, one to a different world and then another to the world you want. You do not need to complete the first respawn; it only matters that you send two packets.

Set Head Rotation

Changes the direction an entity's head is facing.

While sending the Entity Look packet changes the vertical rotation of the head, sending this packet appears to be necessary to rotate the head horizontally.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x3F	Play	Client	Entity ID	VarInt
			Head Yaw	Angle	New angle, not a delta.

Update Section Blocks

Fired whenever 2 or more blocks are changed within the same chunk on the same tick.

Changing blocks in chunks not loaded by the client is unsafe (see note on Block Update).

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x40	Play	Client	Chunk section position	Long	Chunk section coordinate (encoded chunk x and z with each 22 bits, and section y with 20 bits, from left to right).
			Suppress Light Updates	Boolean	Whether to ignore light updates caused by the contained changes. Always inverse the preceding Update Light packet's "Trust Edges" bool
			Blocks array size	VarInt	Number of elements in the following array.
			Blocks	Array of VarLong	Each entry is composed of the block state id, shifted left by 12, and the relative block position in the chunk section (4 bits for x, z, and y, from left to right).

Chunk section position is encoded:

((sectionX & 0x3FFFFF) << 42) | (sectionY & 0xFFFFF) | ((sectionZ & 0x3FFFFF) << 20);

and decoded:

sectionX = long >> 42;
sectionY = long << 44 >> 44;
sectionZ = long << 22 >> 42;

Blocks are encoded:

blockStateId << 12 | (blockLocalX << 8 | blockLocalZ << 4 | blockLocalY)
//Uses the local position of the given block position relative to its respective chunk section

Select Advancements Tab

Sent by the server to indicate that the client should switch advancement tab. Sent either when the client switches tab in the GUI or when an advancement in another tab is made.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x41	Play	Client	Has id	Boolean	Indicates if the next field is present.
			Optional Identifier	String (32767)	See below.

The Identifier can be one of the following:

Optional Identifier
minecraft:story/root
minecraft:nether/root
minecraft:end/root
minecraft:adventure/root
minecraft:husbandry/root

If no or an invalid identifier is sent, the client will switch to the first tab in the GUI.

Server Data

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x42	Play	Client	Has MOTD	Boolean
			MOTD	Optional Chat
			Has Icon	Boolean
			Icon	Optional String (32767)	Icon PNG base64 String
			Previews Chat	Boolean
			Enforces Secure Chat	Boolean

Set Action Bar Text

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x43	Play	Client	Action bar text	Chat	Displays a message above the hotbar (the same as position 2 in Player Chat Message.

Set Border Center

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x44	Play	Client	X	Double
			Z	Double

Set Border Lerp Size

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x45	Play	Client	Old Diameter	Double	Current length of a single side of the world border, in meters.
			New Diameter	Double	Target length of a single side of the world border, in meters.
			Speed	VarLong	Number of real-time milliseconds until New Diameter is reached. It appears that Notchian server does not sync world border speed to game ticks, so it gets out of sync with server lag. If the world border is not moving, this is set to 0.

Set Border Size

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x46	Play	Client	Diameter	Double	Length of a single side of the world border, in meters.

Set Border Warning Delay

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x47	Play	Client	Warning Time	VarInt	In seconds as set by /worldborder warning time.

Set Border Warning Distance

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x48	Play	Client	Warning Blocks	VarInt	In meters.

Set Camera

Sets the entity that the player renders from. This is normally used when the player left-clicks an entity while in spectator mode.

The player's camera will move with the entity and look where it is looking. The entity is often another player, but can be any type of entity. The player is unable to move this entity (move packets will act as if they are coming from the other entity).

If the given entity is not loaded by the player, this packet is ignored. To return control to the player, send this packet with their entity ID.

The Notchian server resets this (sends it back to the default entity) whenever the spectated entity is killed or the player sneaks, but only if they were spectating an entity. It also sends this packet whenever the player switches out of spectator mode (even if they weren't spectating an entity).

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x49	Play	Client	Camera ID	VarInt	ID of the entity to set the client's camera to.

The notchian client also loads certain shaders for given entities:

• Creeper → shaders/post/creeper.json
• Spider (and cave spider) → shaders/post/spider.json
• Enderman → shaders/post/invert.json
• Anything else → the current shader is unloaded

Set Held Item (clientbound)

Sent to change the player's slot selection.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x4A	Play	Client	Slot	Byte	The slot which the player has selected (0–8).

Set Center Chunk

	The following information needs to be added to this page:
	Why is this even needed? Is there a better name for it? My guess is that it's something to do with logical behavior with latency, but it still seems weird.

Updates the client's location. This is used to determine what chunks should remain loaded and if a chunk load should be ignored; chunks outside of the view distance may be unloaded.

Sent whenever the player moves across a chunk border horizontally, and also (according to testing) for any integer change in the vertical axis, even if it doesn't go across a chunk section border.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x4B	Play	Client	Chunk X	VarInt	Chunk X coordinate of the player's position.
			Chunk Z	VarInt	Chunk Z coordinate of the player's position.

Set Render Distance

Sent by the integrated singleplayer server when changing render distance. This packet is sent by the server when the client reappears in the overworld after leaving the end.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x4C	Play	Client	View Distance	VarInt	Render distance (2-32).

Set Default Spawn Position

Sent by the server after login to specify the coordinates of the spawn point (the point at which players spawn at, and which the compass points to). It can be sent at any time to update the point compasses point at.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x4D	Play	Client	Location	Position	Spawn location.
			Angle	Float	The angle at which to respawn at.

Set Display Chat Preview

Sets if chat preview is enabled or disabled on the server. Not used by the server.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x4E	Play	Client	Chat Preview Setting	Boolean

Display Objective

This is sent to the client when it should display a scoreboard.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x4F	Play	Client	Position	Byte	The position of the scoreboard. 0: list, 1: sidebar, 2: below name, 3 - 18: team specific sidebar, indexed as 3 + team color.
			Score Name	String (16)	The unique name for the scoreboard to be displayed.

Set Entity Metadata

Updates one or more metadata properties for an existing entity. Any properties not included in the Metadata field are left unchanged.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x50	Play	Client	Entity ID	VarInt
			Metadata	Entity Metadata

Link Entities

This packet is sent when an entity has been leashed to another entity.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x51	Play	Client	Attached Entity ID	Int	Attached entity's EID.
			Holding Entity ID	Int	ID of the entity holding the lead. Set to -1 to detach.

Set Entity Velocity

Velocity is believed to be in units of 1/8000 of a block per server tick (50ms); for example, -1343 would move (-1343 / 8000) = −0.167875 blocks per tick (or −3,3575 blocks per second).

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x52	Play	Client	Entity ID	VarInt
			Velocity X	Short	Velocity on the X axis.
			Velocity Y	Short	Velocity on the Y axis.
			Velocity Z	Short	Velocity on the Z axis.

Set Equipment

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x53	Play	Client	Entity ID		VarInt		Entity's EID.
			Equipment	Slot	Array	Byte Enum	Equipment slot. 0: main hand, 1: off hand, 2–5: armor slot (2: boots, 3: leggings, 4: chestplate, 5: helmet). Also has the top bit set if another entry follows, and otherwise unset if this is the last item in the array.
				Item		Slot

Set Experience

Sent by the server when the client should change experience levels.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x54	Play	Client	Experience bar	Float	Between 0 and 1.
			Level	VarInt
			Total Experience	VarInt	See Experience#Leveling up on the Minecraft Wiki for Total Experience to Level conversion.

Set Health

Sent by the server to set the health of the player it is sent to.

Food saturation acts as a food “overcharge”. Food values will not decrease while the saturation is over zero. Players logging in automatically get a saturation of 5.0. Eating food increases the saturation as well as the food bar.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x55	Play	Client	Health	Float	0 or less = dead, 20 = full HP.
			Food	VarInt	0–20.
			Food Saturation	Float	Seems to vary from 0.0 to 5.0 in integer increments.

Update Objectives

This is sent to the client when it should create a new scoreboard objective or remove one.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x56	Play	Client	Objective Name	String (16)	A unique name for the objective.
			Mode	Byte	0 to create the scoreboard. 1 to remove the scoreboard. 2 to update the display text.
			Objective Value	Optional Chat	Only if mode is 0 or 2. The text to be displayed for the score.
			Type	Optional VarInt enum	Only if mode is 0 or 2. 0 = "integer", 1 = "hearts".

Set Passengers

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x57	Play	Client	Entity ID	VarInt	Vehicle's EID.
			Passenger Count	VarInt	Number of elements in the following array.
			Passengers	Array of VarInt	EIDs of entity's passengers.

Update Teams

Creates and updates teams.

Packet ID	State	Bound To	Field Name		Field Type	Notes
0x58	Play	Client	Team Name		String (16)	A unique name for the team. (Shared with scoreboard).
			Mode		Byte	Determines the layout of the remaining packet.
			0: create team	Team Display Name	Chat
				Friendly Flags	Byte	Bit mask. 0x01: Allow friendly fire, 0x02: can see invisible players on same team.
				Name Tag Visibility	String Enum (32)	always, hideForOtherTeams, hideForOwnTeam, never.
				Collision Rule	String Enum (32)	always, pushOtherTeams, pushOwnTeam, never.
				Team Color	VarInt enum	Used to color the name of players on the team; see below.
				Team Prefix	Chat	Displayed before the names of players that are part of this team.
				Team Suffix	Chat	Displayed after the names of players that are part of this team.
				Entity Count	VarInt	Number of elements in the following array.
				Entities	Array of String (40)	Identifiers for the entities in this team. For players, this is their username; for other entities, it is their UUID.
			1: remove team	no fields	no fields
			2: update team info	Team Display Name	Chat
				Friendly Flags	Byte	Bit mask. 0x01: Allow friendly fire, 0x02: can see invisible entities on same team.
				Name Tag Visibility	String Enum (32)	always, hideForOtherTeams, hideForOwnTeam, never
				Collision Rule	String Enum (32)	always, pushOtherTeams, pushOwnTeam, never
				Team Color	VarInt enum	Used to color the name of players on the team; see below.
				Team Prefix	Chat	Displayed before the names of players that are part of this team.
				Team Suffix	Chat	Displayed after the names of players that are part of this team.
			3: add entities to team	Entity Count	VarInt	Number of elements in the following array.
				Entities	Array of String (40)	Identifiers for the added entities. For players, this is their username; for other entities, it is their UUID.
			4: remove entities from team	Entity Count	VarInt	Number of elements in the following array.
				Entities	Array of String (40)	Identifiers for the removed entities. For players, this is their username; for other entities, it is their UUID.

Team Color: The color of a team defines how the names of the team members are visualized; any formatting code can be used. The following table lists all the possible values.

ID	Formatting
0-15	Color formatting, same values as Chat colors.
16	Obfuscated
17	Bold
18	Strikethrough
19	Underlined
20	Italic
21	Reset

Update Score

This is sent to the client when it should update a scoreboard item.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x59	Play	Client	Entity Name	String (40)	The entity whose score this is. For players, this is their username; for other entities, it is their UUID.
			Action	VarInt Enum	0 to create/update an item. 1 to remove an item.
			Objective Name	String (16)	The name of the objective the score belongs to.
			Value	Optional VarInt	The score to be displayed next to the entry. Only sent when Action does not equal 1.

Set Simulation Distance

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x5A	Play	Client	Simulation Distance	VarInt	The distance that the client will process specific things, such as entities.

Set Subtitle Text

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x5B	Play	Client	Subtitle Text	Chat

Update Time

Time is based on ticks, where 20 ticks happen every second. There are 24000 ticks in a day, making Minecraft days exactly 20 minutes long.

The time of day is based on the timestamp modulo 24000. 0 is sunrise, 6000 is noon, 12000 is sunset, and 18000 is midnight.

The default SMP server increments the time by 20 every second.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x5C	Play	Client	World Age	Long	In ticks; not changed by server commands.
			Time of day	Long	The world (or region) time, in ticks. If negative the sun will stop moving at the Math.abs of the time.

Set Title Text

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x5D	Play	Client	Title Text	Chat

Set Title Animation Times

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x5E	Play	Client	Fade In	Int	Ticks to spend fading in.
			Stay	Int	Ticks to keep the title displayed.
			Fade Out	Int	Ticks to spend fading out, not when to start fading out.

Entity Sound Effect

Plays a sound effect from an entity.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x5F	Play	Client	Sound ID	VarInt	ID of hardcoded sound event (events).
			Sound Category	VarInt Enum	The category that this sound will be played from (current categories).
			Entity ID	VarInt
			Volume	Float	1.0 is 100%, capped between 0.0 and 1.0 by Notchian clients.
			Pitch	Float	Float between 0.5 and 2.0 by Notchian clients.

Sound Effect

This packet is used to play a number of hardcoded sound events. For custom sounds, use Custom Sound Effect.

Numeric sound effect IDs are liable to change between versions

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x60	Play	Client	Sound ID	VarInt	ID of hardcoded sound event (events).
			Sound Category	VarInt Enum	The category that this sound will be played from (current categories).
			Effect Position X	Int	Effect X multiplied by 8 (fixed-point number with only 3 bits dedicated to the fractional part).
			Effect Position Y	Int	Effect Y multiplied by 8 (fixed-point number with only 3 bits dedicated to the fractional part).
			Effect Position Z	Int	Effect Z multiplied by 8 (fixed-point number with only 3 bits dedicated to the fractional part).
			Volume	Float	1.0 is 100%, capped between 0.0 and 1.0 by Notchian clients.
			Pitch	Float	Float between 0.5 and 2.0 by Notchian clients.
			Seed	long	Seed used to pick sound variant.

Stop Sound

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x61	Play	Client	Flags	Byte	Controls which fields are present.
			Source	Optional VarInt enum	Only if flags is 3 or 1 (bit mask 0x1). See below. If not present, then sounds from all sources are cleared.
			Sound	Optional Identifier	Only if flags is 2 or 3 (bit mask 0x2). A sound effect name, see Custom Sound Effect. If not present, then all sounds are cleared.

Categories:

Name	Value
master	0
music	1
record	2
weather	3
block	4
hostile	5
neutral	6
player	7
ambient	8
voice	9

System Chat Message

Identifying the difference between Chat/System Message is important as it helps respect the user's chat visibility options. See processing chat for more info about these positions.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x62	Play	Client	JSON Data	Chat	Limited to 262144 bytes.
			Overlay	Boolean	Whether the message is an actionbar or chat message.

Set Tab List Header And Footer

This packet may be used by custom servers to display additional information above/below the player list. It is never sent by the Notchian server.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x63	Play	Client	Header	Chat	To remove the header, send a empty text component: {"text":""}.
			Footer	Chat	To remove the footer, send a empty text component: {"text":""}.

Tag Query Response

Sent in response to Query Block Entity Tag or Query Entity Tag.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x64	Play	Client	Transaction ID	VarInt	Can be compared to the one sent in the original query packet.
			NBT	NBT Tag	The NBT of the block or entity. May be a TAG_END (0) in which case no NBT is present.

Pickup Item

Sent by the server when someone picks up an item lying on the ground — its sole purpose appears to be the animation of the item flying towards you. It doesn't destroy the entity in the client memory, and it doesn't add it to your inventory. The server only checks for items to be picked up after each Set Player Position (and Set Player Position And Rotation) packet sent by the client. The collector entity can be any entity; it does not have to be a player. The collected entity also can be any entity, but the Notchian server only uses this for items, experience orbs, and the different varieties of arrows.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x65	Play	Client	Collected Entity ID	VarInt
			Collector Entity ID	VarInt
			Pickup Item Count	VarInt	Seems to be 1 for XP orbs, otherwise the number of items in the stack.

Teleport Entity

This packet is sent by the server when an entity moves more than 8 blocks.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x66	Play	Client	Entity ID	VarInt
			X	Double
			Y	Double
			Z	Double
			Yaw	Angle	(Y Rot)New angle, not a delta.
			Pitch	Angle	(X Rot)New angle, not a delta.
			On Ground	Boolean

Update Advancements

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x67	Play	Client	Reset/Clear		Boolean		Whether to reset/clear the current advancements.
			Mapping size		VarInt		Size of the following array.
			Advancement mapping	Key	Array	Identifier	The identifier of the advancement.
				Value		Advancement	See below
			List size		VarInt		Size of the following array.
			Identifiers		Array of Identifier		The identifiers of the advancements that should be removed.
			Progress size		VarInt		Size of the following array.
			Progress mapping	Key	Array	Identifier	The identifier of the advancement.
				Value		Advancement progress	See below.

Advancement structure:

Field Name		Field Type		Notes
Has parent		Boolean		Indicates whether the next field exists.
Parent id		Optional Identifier		The identifier of the parent advancement.
Has display		Boolean		Indicates whether the next field exists.
Display data		Optional advancement display		See below.
Number of criteria		VarInt		Size of the following array.
Criteria	Key	Array	Identifier	The identifier of the criterion.
	Value		Void	There is no content written here. Perhaps this will be expanded in the future?
Array length		VarInt		Number of arrays in the following array.
Requirements	Array length 2	Array	VarInt	Number of elements in the following array.
	Requirement		Array of String	Array of required criteria.

Advancement display:

Field Name	Field Type	Notes
Title	Chat
Description	Chat
Icon	Slot
Frame type	VarInt enum	0 = task, 1 = challenge, 2 = goal.
Flags	Integer	0x01: has background texture; 0x02: show_toast; 0x04: hidden.
Background texture	Optional Identifier	Background texture location. Only if flags indicates it.
X coord	Float
Y coord	Float

Advancement progress:

Field Name		Field Type		Notes
Size		VarInt		Size of the following array.
Criteria	Criterion identifier	Array	Identifier	The identifier of the criterion.
	Criterion progress		Criterion progress

Criterion progress:

Field Name	Field Type	Notes
Achieved	Boolean	If true, next field is present.
Date of achieving	Optional Long	As returned by Date.getTime.

Update Attributes

Sets attributes on the given entity.

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x68	Play	Client	Entity ID		VarInt
			Number Of Properties		VarInt		Number of elements in the following array.
			Property	Key	Array	Identifier	See below.
				Value		Double	See below.
				Number Of Modifiers		VarInt	Number of elements in the following array.
				Modifiers		Array of Modifier Data	See Attribute#Modifiers. Modifier Data defined below.

Known Key values (see also Attribute#Modifiers):

Key	Default	Min	Max	Label
generic.max_health	20.0	1.0	1024.0	Max Health.
generic.follow_range	32.0	0.0	2048.0	Follow Range.
generic.knockback_resistance	0.0	0.0	1.0	Knockback Resistance.
generic.movement_speed	0.7	0.0	1024.0	Movement Speed.
generic.flying_speed	0.4	0.0	1024.0	Flying Speed.
generic.attack_damage	2.0	0.0	2048.0	Attack Damage.
generic.attack_knockback	0.0	0.0	5.0	—
generic.attack_speed	4.0	0.0	1024.0	Attack Speed.
generic.armor	0.0	0.0	30.0	Armor.
generic.armor_toughness	0.0	0.0	20.0	Armor Toughness.
generic.luck	0.0	-1024.0	1024.0	Luck.
zombie.spawn_reinforcements	0.0	0.0	1.0	Spawn Reinforcements Chance.
horse.jump_strength	0.7	0.0	2.0	Jump Strength.
generic.reachDistance	5.0	0.0	1024.0	Player Reach Distance (Forge only).
forge.swimSpeed	1.0	0.0	1024.0	Swimming Speed (Forge only).

Modifier Data structure:

Field Name	Field Type	Notes
UUID	UUID
Amount	Double	May be positive or negative.
Operation	Byte	See below.

The operation controls how the base value of the modifier is changed.

• 0: Add/subtract amount
• 1: Add/subtract amount percent of the current value
• 2: Multiply by amount percent

All of the 0's are applied first, and then the 1's, and then the 2's.

Entity Effect

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x69	Play	Client	Entity ID	VarInt
			Effect ID	VarInt	See this table.
			Amplifier	Byte	Notchian client displays effect level as Amplifier + 1.
			Duration	VarInt	Duration in ticks.
			Flags	Byte	Bit field, see below.
			Has Factor Data	boolean	Used in DARKNESS effect
			Factor Codec	NBT Tag	See below

Within flags:

• 0x01: Is ambient - was the effect spawned from a beacon? All beacon-generated effects are ambient. Ambient effects use a different icon in the HUD (blue border rather than gray). If all effects on an entity are ambient, the "Is potion effect ambient" living metadata field should be set to true. Usually should not be enabled.
• 0x02: Show particles - should all particles from this effect be hidden? Effects with particles hidden are not included in the calculation of the effect color, and are not rendered on the HUD (but are still rendered within the inventory). Usually should be enabled.
• 0x04: Show icon - should the icon be displayed on the client? Usually should be enabled.

Factor Data

Name	Type	Notes
padding_duration	TAG_INT
factor_start	TAG_FLOAT
factor_target	TAG_FLOAT
factor_current	TAG_FLOAT
effect_changed_timestamp	TAG_INT
factor_previous_frame	TAG_FLOAT
had_effect_last_tick	TAG_BOOLEAN

Update Recipes

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x6A	Play	Client	Num Recipes		VarInt		Number of elements in the following array.
			Recipe	Type	Array	Identifier	The recipe type, see below.
				Recipe ID		Identifier
				Data		Optional, varies	Additional data for the recipe. For some types, there will be no data.

Recipe types:

Type	Description	Data
crafting_shapeless	Shapeless crafting recipe. All items in the ingredient list must be present, but in any order/slot.	As follows: Name Type Description Group String Used to group similar recipes together in the recipe book. Tag is present in recipe JSON. Ingredient count VarInt Number of elements in the following array. Ingredients Array of Ingredient. Result Slot
crafting_shaped	Shaped crafting recipe. All items must be present in the same pattern (which may be flipped horizontally or translated).	As follows: Name Type Description Width VarInt Height VarInt Group String Used to group similar recipes together in the recipe book. Tag is present in recipe JSON. Ingredients Array of Ingredient Length is width * height. Indexed by x + (y * width). Result Slot
crafting_special_armordye	Recipe for dying leather armor	None
crafting_special_bookcloning	Recipe for copying contents of written books
crafting_special_mapcloning	Recipe for copying maps
crafting_special_mapextending	Recipe for adding paper to maps
crafting_special_firework_rocket	Recipe for making firework rockets
crafting_special_firework_star	Recipe for making firework stars
crafting_special_firework_star_fade	Recipe for making firework stars fade between multiple colors
crafting_special_repairitem	Recipe for repairing items via crafting
crafting_special_tippedarrow	Recipe for crafting tipped arrows
crafting_special_bannerduplicate	Recipe for copying banner patterns
crafting_special_banneraddpattern	Recipe for adding patterns to banners
crafting_special_shielddecoration	Recipe for applying a banner's pattern to a shield
crafting_special_shulkerboxcoloring	Recipe for recoloring a shulker box
crafting_special_suspiciousstew
smelting	Smelting recipe	As follows: Name Type Description Group String Used to group similar recipes together in the recipe book. Ingredient Ingredient Result Slot Experience Float Cooking time VarInt
blasting	Blast furnace recipe
smoking	Smoker recipe
campfire_cooking	Campfire recipe
stonecutting	Stonecutter recipe	As follows: Name Type Description Group String Used to group similar recipes together in the recipe book. Tag is present in recipe JSON. Ingredient Ingredient Result Slot
smithing	Smithing table recipe	As follows: Name Type Description Base Ingredient First item. Addition Ingredient Second item. Result Slot

Ingredient is defined as:

Name	Type	Description
Count	VarInt	Number of elements in the following array.
Items	Array of Slot	Any item in this array may be used for the recipe. The count of each item should be 1.

Update Tags

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x6B	Play	Client	Length of the array		VarInt
			Array of tags	Tag type	Array	Identifier	Tag identifier (Vanilla required tags are minecraft:block, minecraft:item, minecraft:fluid, minecraft:entity_type, and minecraft:game_event)
				Array of Tag		(See below)

Tags look like:

Field Name		Field Type		Notes
Length		VarInt		Number of elements in the following array
Tags	Tag name	Array	Identifier
	Count		VarInt	Number of elements in the following array
	Entries		Array of VarInt	Numeric ID of the given type (block, item, etc.).

More information on tags is available at: https://minecraft.gamepedia.com/Tag

And a list of all tags is here: https://minecraft.gamepedia.com/Tag#List_of_tags

Serverbound

Confirm Teleportation

Sent by client as confirmation of Synchronize Player Position.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x00	Play	Server	Teleport ID	VarInt	The ID given by the Synchronize Player Position packet.

Query Block Entity Tag

Used when Shift+F3+I is pressed while looking at a block.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x01	Play	Server	Transaction ID	VarInt	An incremental ID so that the client can verify that the response matches.
			Location	Position	The location of the block to check.

Change Difficulty

Must have at least op level 2 to use. Appears to only be used on singleplayer; the difficulty buttons are still disabled in multiplayer.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x02	Play	Server	New difficulty	Byte	0: peaceful, 1: easy, 2: normal, 3: hard .

Message Acknowledgment

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x03	Play	Server	Has Data	Boolean	If true, all of the following fields are present.
			Profile ID	UUID
			Last Signature Length	VarInt	Length of the following array.
			Last Signature	Byte Array

Chat Command

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x04	Play	Server
			Command		String		The command typed by the client.
			Timestamp		Long		The timestamp that the command was executed.
			Salt		Long		The salt for the following argument signatures.
			Array length		VarInt		The length of the following array
			Array of argument signatures	Argument name	Array	String	The name of the argument that is signed by the following signature.
				Signature length		VarInt	The length of the follow byte array
				Signature		Byte Array	The signature that verifies the argument.
			Signed Preview		Boolean

Chat Message

Used to send a chat message to the server. The message may not be longer than 256 characters or else the server will kick the client.

The server will broadcast the same chat message to all players on the server (including the player that sent the message), prepended with player's name. Specifically, it will respond with a translate chat component, "chat.type.text" with the first parameter set to the display name of the player (including some chat component logic to support clicking the name to send a PM) and the second parameter set to the message. See processing chat for more information.

Packet ID	State	Bound To	Field Name		Field Type	Notes
0x05	Play	Server	Message		String (256 chars)
			Timestamp		Instant
			Salt		Long	The salt used to verify the signature hash.
			Signature Length		VarInt	The length of the following array.
			Signature		Byte Array	The signature used to verify the chat message's authentication.
			Signed Preview		Boolean
			Array length		VarInt	The length of previously seen messages array.
			Array of previously seen messages	User	UUID	Previous message sender's ID.
				Message signature	Byte Array	Cryptography, the signature consists of the previous sender's UUID, Timestamp and Original Chat Context.
			Has last message		Boolean	True if there is one more element with the same format as the list. In notchian clients this is only sent if the last message wasn't rendered by the client.
			Last message	User	Optional UUID	Only if Has last message is true. Same as above.
				Message signature	Optional Byte Array	Only if Has last message is true. Same as above.

Chat Preview (serverbound)

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x06	Play	Server	Query	Integer
			Message	String (256)

Client Command

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x07	Play	Server	Action ID	VarInt Enum	See below

Action ID values:

Action ID	Action	Notes
0	Perform respawn	Sent when the client is ready to complete login and when the client is ready to respawn after death.
1	Request stats	Sent when the client opens the Statistics menu.

Client Information

Sent when the player connects, or when settings are changed.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x08	Play	Server	Locale	String (16)	e.g. en_GB.
			View Distance	Byte	Client-side render distance, in chunks.
			Chat Mode	VarInt Enum	0: enabled, 1: commands only, 2: hidden. See processing chat for more information.
			Chat Colors	Boolean	“Colors” multiplayer setting. Can the chat be colored?
			Displayed Skin Parts	Unsigned Byte	Bit mask, see below.
			Main Hand	VarInt Enum	0: Left, 1: Right.
			Enable text filtering	Boolean	Enables filtering of text on signs and written book titles. Currently always false (i.e. the filtering is disabled)
			Allow server listings	Boolean	Servers usually list online players, this option should let you not show up in that list.

Displayed Skin Parts flags:

• Bit 0 (0x01): Cape enabled
• Bit 1 (0x02): Jacket enabled
• Bit 2 (0x04): Left Sleeve enabled
• Bit 3 (0x08): Right Sleeve enabled
• Bit 4 (0x10): Left Pants Leg enabled
• Bit 5 (0x20): Right Pants Leg enabled
• Bit 6 (0x40): Hat enabled

The most significant bit (bit 7, 0x80) appears to be unused.

Command Suggestions Request

Sent when the client needs to tab-complete a minecraft:ask_server suggestion type.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x09	Play	Server	Transaction Id	VarInt	The id of the transaction that the server will send back to the client in the response of this packet. Client generates this and increments it each time it sends another tab completion that doesn't get a response.
			Text	String (32500)	All text behind the cursor without the / (e.g. to the left of the cursor in left-to-right languages like English).

Click Container Button

Used when clicking on window buttons. Until 1.14, this was only used by enchantment tables.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x0A	Play	Server	Window ID	Byte	The ID of the window sent by Open Screen.
			Button ID	Byte	Meaning depends on window type; see below.

Window type	ID	Meaning
Enchantment Table	0	Topmost enchantment.
	1	Middle enchantment.
	2	Bottom enchantment.
Lectern	1	Previous page (which does give a redstone output).
	2	Next page.
	3	Take Book.
	100+page	Opened page number - 100 + number.
Stonecutter	Recipe button number - 4*row + col. Depends on the item.
Loom	Recipe button number - 4*row + col. Depends on the item.

Click Container

This packet is sent by the client when the player clicks on a slot in a window.

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x0B	Play	Server	Window ID		Unsigned Byte		The ID of the window which was clicked. 0 for player inventory.
			State ID		VarInt		The last recieved State ID from either a Set Container Slot or a Set Container Content packet
			Slot		Short		The clicked slot number, see below.
			Button		Byte		The button used in the click, see below.
			Mode		VarInt Enum		Inventory operation mode, see below.
			Length of the array		VarInt
			Array of slots	Slot number	Array	Short
				Slot data		Slot	New data for this slot
			Carried item		Slot		Item carried by the cursor. Has to be empty (item ID = -1) for drop mode, otherwise nothing will happen.

See Inventory for further information about how slots are indexed.

When right-clicking on a stack of items, half the stack will be picked up and half left in the slot. If the stack is an odd number, the half left in the slot will be smaller of the amounts.

The distinct type of click performed by the client is determined by the combination of the Mode and Button fields.

Mode	Button	Slot	Trigger
0	0	Normal	Left mouse click
	1	Normal	Right mouse click
	0	-999	Left click outside inventory (drop cursor stack)
	1	-999	Right click outside inventory (drop cursor single item)
1	0	Normal	Shift + left mouse click
	1	Normal	Shift + right mouse click (identical behavior)
2	0	Normal	Number key 1
	1	Normal	Number key 2
	2	Normal	Number key 3
	⋮	⋮	⋮
	8	Normal	Number key 9
	40	Normal	Offhand swap key F
3	2	Normal	Middle click, only defined for creative players in non-player inventories.
4	0	Normal*	Drop key (Q) (* Clicked item is always empty)
	1	Normal*	Control + Drop key (Q) (* Clicked item is always empty)
5	0	-999	Starting left mouse drag
	4	-999	Starting right mouse drag
	8	-999	Starting middle mouse drag, only defined for creative players in non-player inventories.
	1	Normal	Add slot for left-mouse drag
	5	Normal	Add slot for right-mouse drag
	9	Normal	Add slot for middle-mouse drag, only defined for creative players in non-player inventories.
	2	-999	Ending left mouse drag
	6	-999	Ending right mouse drag
	10	-999	Ending middle mouse drag, only defined for creative players in non-player inventories.
6	0	Normal	Double click

Starting from version 1.5, “painting mode” is available for use in inventory windows. It is done by picking up stack of something (more than 1 item), then holding mouse button (left, right or middle) and dragging held stack over empty (or same type in case of right button) slots. In that case client sends the following to server after mouse button release (omitting first pickup packet which is sent as usual):

1. packet with mode 5, slot -999, button (0 for left | 4 for right);
2. packet for every slot painted on, mode is still 5, button (1 | 5);
3. packet with mode 5, slot -999, button (2 | 6);

If any of the painting packets other than the “progress” ones are sent out of order (for example, a start, some slots, then another start; or a left-click in the middle) the painting status will be reset.

Close Container (serverbound)

This packet is sent by the client when closing a window.

Notchian clients send a Close Window packet with Window ID 0 to close their inventory even though there is never an Open Screen packet for the inventory.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x0C	Play	Server	Window ID	Unsigned Byte	This is the ID of the window that was closed. 0 for player inventory.

Plugin Message (serverbound)

Main article: Plugin channels

Mods and plugins can use this to send their data. Minecraft itself uses some plugin channels. These internal channels are in the minecraft namespace.

More documentation on this: https://dinnerbone.com/blog/2012/01/13/minecraft-plugin-channels-messaging/

Note that the length of Data is known only from the packet length, since the packet has no length field of any kind.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x0D	Play	Server	Channel	Identifier	Name of the plugin channel used to send the data.
			Data	Byte Array (32767)	Any data, depending on the channel. minecraft: channels are documented here. The length of this array must be inferred from the packet length.

In Notchian server, the maximum data length is 32767 bytes.

Edit Book

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x0E	Play	Server	Slot	VarInt	The hotbar slot where the written book is located
			Count	VarInt	Number of elements in the following array
			Entries	Array of Strings	Text from each page.
			Has title	Boolean	If true, the next field is present.
			Title	Optional String	Title of book.

When editing a draft, the NBT section of the Slot contains this:

TAG_Compound(''): 1 entry
{
  TAG_List('pages'): 2 entries
  {
    TAG_String(0): 'Something on Page 1'
    TAG_String(1): 'Something on Page 2'
  }
}

When signing the book, it instead looks like this:

TAG_Compound(''): 3 entires
{
  TAG_String('author'): 'Steve'
  TAG_String('title'): 'A Wonderful Book'
  TAG_List('pages'): 2 entries
  {
    TAG_String(0): 'Something on Page 1'
    TAG_String(1): 'Something on Page 2'
  }
}

Query Entity Tag

Used when Shift+F3+I is pressed while looking at an entity.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x0F	Play	Server	Transaction ID	VarInt	An incremental ID so that the client can verify that the response matches.
			Entity ID	VarInt	The ID of the entity to query.

Interact

This packet is sent from the client to the server when the client attacks or right-clicks another entity (a player, minecart, etc).

A Notchian server only accepts this packet if the entity being attacked/used is visible without obstruction and within a 4-unit radius of the player's position.

The target X, Y, and Z fields represent the difference between the vector location of the cursor at the time of the packet and the entity's position.

Note that middle-click in creative mode is interpreted by the client and sent as a Set Creative Mode Slot packet instead.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x10	Play	Server	Entity ID	VarInt	The ID of the entity to interact.
			Type	VarInt Enum	0: interact, 1: attack, 2: interact at.
			Target X	Optional Float	Only if Type is interact at.
			Target Y	Optional Float	Only if Type is interact at.
			Target Z	Optional Float	Only if Type is interact at.
			Hand	Optional VarInt Enum	Only if Type is interact or interact at; 0: main hand, 1: off hand.
			Sneaking	Boolean	If the client is sneaking.

Jigsaw Generate

Sent when Generate is pressed on the Jigsaw Block interface.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x11	Play	Server	Location	Position	Block entity location.
			Levels	VarInt	Value of the levels slider/max depth to generate.
			Keep Jigsaws	Boolean

Keep Alive (serverbound)

The server will frequently send out a keep-alive, each containing a random ID. The client must respond with the same packet.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x12	Play	Server	Keep Alive ID	Long

Lock Difficulty

Must have at least op level 2 to use. Appears to only be used on singleplayer; the difficulty buttons are still disabled in multiplayer.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x13	Play	Server	Locked	Boolean

Set Player Position

Updates the player's XYZ position on the server.

Checking for moving too fast is achieved like this:

• Each server tick, the player's current position is stored
• When a player moves, the changes in x, y, and z coordinates are compared with the positions from the previous tick (Δx, Δy, Δz)
• Total movement distance squared is computed as Δx² + Δy² + Δz²
• The expected movement distance squared is computed as velocityX² + velocityY² + velocityZ²
• If the total movement distance squared value minus the expected movement distance squared value is more than 100 (300 if the player is using an elytra), they are moving too fast.

If the player is moving too fast, it will be logged that "<player> moved too quickly! " followed by the change in x, y, and z, and the player will be teleported back to their current (before this packet) serverside position.

Also, if the absolute value of X or the absolute value of Z is a value greater than 3.2×10⁷, or X, Y, or Z are not finite (either positive infinity, negative infinity, or NaN), the client will be kicked for “Invalid move player packet received”.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x14	Play	Server	X	Double	Absolute position.
			Feet Y	Double	Absolute feet position, normally Head Y - 1.62.
			Z	Double	Absolute position.
			On Ground	Boolean	True if the client is on the ground, false otherwise.

Set Player Position and Rotation

A combination of Move Player Rotation and Move Player Position.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x15	Play	Server	X	Double	Absolute position.
			Feet Y	Double	Absolute feet position, normally Head Y - 1.62.
			Z	Double	Absolute position.
			Yaw	Float	Absolute rotation on the X Axis, in degrees.
			Pitch	Float	Absolute rotation on the Y Axis, in degrees.
			On Ground	Boolean	True if the client is on the ground, false otherwise.

Set Player Rotation

The unit circle for yaw

The unit circle of yaw, redrawn

Updates the direction the player is looking in.

Yaw is measured in degrees, and does not follow classical trigonometry rules. The unit circle of yaw on the XZ-plane starts at (0, 1) and turns counterclockwise, with 90 at (-1, 0), 180 at (0,-1) and 270 at (1, 0). Additionally, yaw is not clamped to between 0 and 360 degrees; any number is valid, including negative numbers and numbers greater than 360.

Pitch is measured in degrees, where 0 is looking straight ahead, -90 is looking straight up, and 90 is looking straight down.

The yaw and pitch of player (in degrees), standing at point (x0, y0, z0) and looking towards point (x, y, z) can be calculated with:

dx = x-x0
dy = y-y0
dz = z-z0
r = sqrt( dx*dx + dy*dy + dz*dz )
yaw = -atan2(dx,dz)/PI*180
if yaw < 0 then
    yaw = 360 + yaw
pitch = -arcsin(dy/r)/PI*180

You can get a unit vector from a given yaw/pitch via:

x = -cos(pitch) * sin(yaw)
y = -sin(pitch)
z =  cos(pitch) * cos(yaw)

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x16	Play	Server	Yaw	Float	Absolute rotation on the X Axis, in degrees.
			Pitch	Float	Absolute rotation on the Y Axis, in degrees.
			On Ground	Boolean	True if the client is on the ground, false otherwise.

Set Player On Ground

This packet as well as Set Player Position, Set Player Rotation, and Set Player Position and Rotation are called the “serverbound movement packets”. Vanilla clients will send Move Player Position once every 20 ticks even for a stationary player.

This packet is used to indicate whether the player is on ground (walking/swimming), or airborne (jumping/falling).

When dropping from sufficient height, fall damage is applied when this state goes from false to true. The amount of damage applied is based on the point where it last changed from true to false. Note that there are several movement related packets containing this state.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x17	Play	Server	On Ground	Boolean	True if the client is on the ground, false otherwise.

Move Vehicle (serverbound)

Sent when a player moves in a vehicle. Fields are the same as in Set Player Position and Rotation. Note that all fields use absolute positioning and do not allow for relative positioning.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x18	Play	Server	X	Double	Absolute position (X coordinate).
			Y	Double	Absolute position (Y coordinate).
			Z	Double	Absolute position (Z coordinate).
			Yaw	Float	Absolute rotation on the vertical axis, in degrees.
			Pitch	Float	Absolute rotation on the horizontal axis, in degrees.

Paddle Boat

Used to visually update whether boat paddles are turning. The server will update the Boat entity metadata to match the values here.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x19	Play	Server	Left paddle turning	Boolean
			Right paddle turning	Boolean

Right paddle turning is set to true when the left button or forward button is held, left paddle turning is set to true when the right button or forward button is held.

Pick Item

Used to swap out an empty space on the hotbar with the item in the given inventory slot. The Notchain client uses this for pick block functionality (middle click) to retrieve items from the inventory.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x1A	Play	Server	Slot to use	VarInt	See Inventory.

The server will first search the player's hotbar for an empty slot, starting from the current slot and looping around to the slot before it. If there are no empty slots, it will start a second search from the current slot and find the first slot that does not contain an enchanted item. If there still are no slots that meet that criteria, then the server will use the currently selected slot.

After finding the appropriate slot, the server swaps the items and then send 3 packets:

• Set Container Slot, with window ID set to -2 and slot set to the newly chosen slot and the item set to the item that is now in that slot (which was previously at the slot the client requested)
• Set Slot, with window ID set to -2 and slot set to the slot the player requested, with the item that is now in that slot and was previously on the hotbar slot
• Set Held Item, with the slot set to the newly chosen slot.

Place Recipe

This packet is sent when a player clicks a recipe in the crafting book that is craftable (white border).

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x1B	Play	Server	Window ID	Byte
			Recipe	Identifier	A recipe ID.
			Make all	Boolean	Affects the amount of items processed; true if shift is down when clicked.

Player Abilities (serverbound)

The vanilla client sends this packet when the player starts/stops flying with the Flags parameter changed accordingly.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x1C	Play	Server	Flags	Byte	Bit mask. 0x02: is flying.

Player Action

Sent when the player mines a block. A Notchian server only accepts digging packets with coordinates within a 6-unit radius between the center of the block and 1.5 units from the player's feet (not their eyes).

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x1D	Play	Server	Status	VarInt Enum	The action the player is taking against the block (see below).
			Location	Position	Block position.
			Face	Byte Enum	The face being hit (see below).
			Sequence	VarInt

Status can be one of seven values:

Value	Meaning	Notes
0	Started digging
1	Cancelled digging	Sent when the player lets go of the Mine Block key (default: left click).
2	Finished digging	Sent when the client thinks it is finished.
3	Drop item stack	Triggered by using the Drop Item key (default: Q) with the modifier to drop the entire selected stack (default: Control or Command, depending on OS). Location is always set to 0/0/0, Face is always set to -Y.
4	Drop item	Triggered by using the Drop Item key (default: Q). Location is always set to 0/0/0, Face is always set to -Y.
5	Shoot arrow / finish eating	Indicates that the currently held item should have its state updated such as eating food, pulling back bows, using buckets, etc. Location is always set to 0/0/0, Face is always set to -Y.
6	Swap item in hand	Used to swap or assign an item to the second hand. Location is always set to 0/0/0, Face is always set to -Y.

The Face field can be one of the following values, representing the face being hit:

Value	Offset	Face
0	-Y	Bottom
1	+Y	Top
2	-Z	North
3	+Z	South
4	-X	West
5	+X	East

Player Command

Sent by the client to indicate that it has performed certain actions: sneaking (crouching), sprinting, exiting a bed, jumping with a horse, and opening a horse's inventory while riding it.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x1E	Play	Server	Entity ID	VarInt	Player ID
			Action ID	VarInt Enum	The ID of the action, see below.
			Jump Boost	VarInt	Only used by the “start jump with horse” action, in which case it ranges from 0 to 100. In all other cases it is 0.

Action ID can be one of the following values:

ID	Action
0	Start sneaking
1	Stop sneaking
2	Leave bed
3	Start sprinting
4	Stop sprinting
5	Start jump with horse
6	Stop jump with horse
7	Open horse inventory
8	Start flying with elytra

Leave bed is only sent when the “Leave Bed” button is clicked on the sleep GUI, not when waking up due today time.

Open horse inventory is only sent when pressing the inventory key (default: E) while on a horse — all other methods of opening a horse's inventory (involving right-clicking or shift-right-clicking it) do not use this packet.

Player Input

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x1F	Play	Server	Sideways	Float	Positive to the left of the player.
			Forward	Float	Positive forward.
			Flags	Unsigned Byte	Bit mask. 0x1: jump, 0x2: unmount.

Also known as 'Input' packet.

Pong (play)

Response to the clientbound packet (Ping) with the same id.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x20	Play	Server	ID	Int	id is the same as the ping packet

Change Recipe Book Settings

Replaces Recipe Book Data, type 1.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x21	Play	Server	Book ID	VarInt enum	0: crafting, 1: furnace, 2: blast furnace, 3: smoker.
			Book Open	Boolean
			Filter Active	Boolean

Set Seen Recipe

Sent when recipe is first seen in recipe book. Replaces Recipe Book Data, type 0.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x22	Play	Server	Recipe ID	Identifier

Rename Item

Sent as a player is renaming an item in an anvil (each keypress in the anvil UI sends a new Rename Item packet). If the new name is empty, then the item loses its custom name (this is different from setting the custom name to the normal name of the item). The item name may be no longer than 50 characters long, and if it is longer than that, then the rename is silently ignored.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x23	Play	Server	Item name	String (32767)	The new name of the item.

Resource Pack (serverbound)

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x24	Play	Server	Result	VarInt Enum	0: successfully loaded, 1: declined, 2: failed download, 3: accepted.

Seen Advancements

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x25	Play	Server	Action	VarInt enum	0: Opened tab, 1: Closed screen.
			Tab ID	Optional identifier	Only present if action is Opened tab.

Select Trade

When a player selects a specific trade offered by a villager NPC.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x26	Play	Server	Selected slot	VarInt	The selected slot in the players current (trading) inventory. (Was a full Integer for the plugin message).

Set Beacon Effect

Changes the effect of the current beacon.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x27	Play	Server
			Has Primary Effect	Boolean
			Primary Effect	VarInt	A Potion ID. (Was a full Integer for the plugin message).
			Has Secondary Effect	Boolean
			Secondary Effect	VarInt	A Potion ID. (Was a full Integer for the plugin message).

Set Held Item (serverbound)

Sent when the player changes the slot selection

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x28	Play	Server	Slot	Short	The slot which the player has selected (0–8).

Program Command Block

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x29	Play	Server
			Location	Position
			Command	String (32767)
			Mode	VarInt enum	One of SEQUENCE (0), AUTO (1), or REDSTONE (2).
			Flags	Byte	0x01: Track Output (if false, the output of the previous command will not be stored within the command block); 0x02: Is conditional; 0x04: Automatic.

Program Command Block Minecart

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x2A	Play	Server	Entity ID	VarInt
			Command	String (32767)
			Track Output	Boolean	If false, the output of the previous command will not be stored within the command block.

Set Creative Mode Slot

While the user is in the standard inventory (i.e., not a crafting bench) in Creative mode, the player will send this packet.

Clicking in the creative inventory menu is quite different from non-creative inventory management. Picking up an item with the mouse actually deletes the item from the server, and placing an item into a slot or dropping it out of the inventory actually tells the server to create the item from scratch. (This can be verified by clicking an item that you don't mind deleting, then severing the connection to the server; the item will be nowhere to be found when you log back in.) As a result of this implementation strategy, the "Destroy Item" slot is just a client-side implementation detail that means "I don't intend to recreate this item.". Additionally, the long listings of items (by category, etc.) are a client-side interface for choosing which item to create. Picking up an item from such listings sends no packets to the server; only when you put it somewhere does it tell the server to create the item in that location.

This action can be described as "set inventory slot". Picking up an item sets the slot to item ID -1. Placing an item into an inventory slot sets the slot to the specified item. Dropping an item (by clicking outside the window) effectively sets slot -1 to the specified item, which causes the server to spawn the item entity, etc.. All other inventory slots are numbered the same as the non-creative inventory (including slots for the 2x2 crafting menu, even though they aren't visible in the vanilla client).

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x2B	Play	Server	Slot	Short	Inventory slot.
			Clicked Item	Slot

Program Jigsaw Block

Sent when Done is pressed on the Jigsaw Block interface.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x2C	Play	Server	Location	Position	Block entity location
			Name	Identifier
			Target	Identifier
			Pool	Identifier
			Final state	String (32767)	"Turns into" on the GUI, final_state in NBT.
			Joint type	String	rollable if the attached piece can be rotated, else aligned.

Program Structure Block

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x2D	Play	Server
			Location	Position	Block entity location.
			Action	VarInt enum	An additional action to perform beyond simply saving the given data; see below.
			Mode	VarInt enum	One of SAVE (0), LOAD (1), CORNER (2), DATA (3).
			Name	String (32767)
			Offset X	Byte	Between -32 and 32.
			Offset Y	Byte	Between -32 and 32.
			Offset Z	Byte	Between -32 and 32.
			Size X	Byte	Between 0 and 32.
			Size Y	Byte	Between 0 and 32.
			Size Z	Byte	Between 0 and 32.
			Mirror	VarInt enum	One of NONE (0), LEFT_RIGHT (1), FRONT_BACK (2).
			Rotation	VarInt enum	One of NONE (0), CLOCKWISE_90 (1), CLOCKWISE_180 (2), COUNTERCLOCKWISE_90 (3).
			Metadata	String (128)
			Integrity	Float	Between 0 and 1.
			Seed	VarLong
			Flags	Byte	0x01: Ignore entities; 0x02: Show air; 0x04: Show bounding box.

Possible actions:

• 0 - Update data
• 1 - Save the structure
• 2 - Load the structure
• 3 - Detect size

The Notchian client uses update data to indicate no special action should be taken (i.e. the done button).

Update Sign

This message is sent from the client to the server when the “Done” button is pushed after placing a sign.

The server only accepts this packet after Open Sign Editor, otherwise this packet is silently ignored.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x2E	Play	Server	Location	Position	Block Coordinates.
			Line 1	String (384)	First line of text in the sign.
			Line 2	String (384)	Second line of text in the sign.
			Line 3	String (384)	Third line of text in the sign.
			Line 4	String (384)	Fourth line of text in the sign.

Swing Arm

Sent when the player's arm swings.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x2F	Play	Server	Hand	VarInt Enum	Hand used for the animation. 0: main hand, 1: off hand.

Teleport To Entity

Teleports the player to the given entity. The player must be in spectator mode.

The Notchian client only uses this to teleport to players, but it appears to accept any type of entity. The entity does not need to be in the same dimension as the player; if necessary, the player will be respawned in the right world. If the given entity cannot be found (or isn't loaded), this packet will be ignored. It will also be ignored if the player attempts to teleport to themselves.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x30	Play	Server	Target Player	UUID	UUID of the player to teleport to (can also be an entity UUID).

Use Item On

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x31	Play	Server	Hand	VarInt Enum	The hand from which the block is placed; 0: main hand, 1: off hand.
			Location	Position	Block position.
			Face	VarInt Enum	The face on which the block is placed (as documented at Player Action).
			Cursor Position X	Float	The position of the crosshair on the block, from 0 to 1 increasing from west to east.
			Cursor Position Y	Float	The position of the crosshair on the block, from 0 to 1 increasing from bottom to top.
			Cursor Position Z	Float	The position of the crosshair on the block, from 0 to 1 increasing from north to south.
			Inside block	Boolean	True when the player's head is inside of a block.
			Sequence	VarInt

Upon placing a block, this packet is sent once.

The Cursor Position X/Y/Z fields (also known as in-block coordinates) are calculated using raytracing. The unit corresponds to sixteen pixels in the default resource pack. For example, let's say a slab is being placed against the south face of a full block. The Cursor Position X will be higher if the player was pointing near the right (east) edge of the face, lower if pointing near the left. The Cursor Position Y will be used to determine whether it will appear as a bottom slab (values 0.0–0.5) or as a top slab (values 0.5-1.0). The Cursor Position Z should be 1.0 since the player was looking at the southernmost part of the block.

Inside block is true when a player's head (specifically eyes) are inside of a block's collision. In 1.13 and later versions, collision is rather complicated and individual blocks can have multiple collision boxes. For instance, a ring of vines has a non-colliding hole in the middle. This value is only true when the player is directly in the box. In practice, though, this value is only used by scaffolding to place in front of the player when sneaking inside of it (other blocks will place behind when you intersect with them -- try with glass for instance).

Use Item

Sent when pressing the Use Item key (default: right click) with an item in hand.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x32	Play	Server	Hand	VarInt Enum	Hand used for the animation. 0: main hand, 1: off hand.
			Sequence	VarInt