Protocol

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Heads up!

This article is about the protocol for the latest stable release of Minecraft computer edition. For the computer edition pre-releases, see Pre-release protocol. For Pocket Edition, see Pocket Minecraft Protocol.

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.freenode.net).

Note: While you may use the contents of this page without restriction to create servers, clients, bots, etc… you still need to provide attribution to #mcdevs if you copy any of the contents of this page for publication elsewhere.

The changes between versions may be viewed at Protocol History.

Contents

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 (Handshaking, 0x00, serverbound) and Login Success (Login, 0x02, clientbound).

Data types

All data sent over the network 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 ≥ 1
≤ 2147483652
A sequence of Unicode scalar values UTF-8 string prefixed with its size in bytes as a VarInt
Chat ≥ 1
≤ 2147483652
See Chat Encoded as a String
VarInt ≥ 1
≤ 5
An integer between -2147483648 and 2147483647 Protocol Buffer Varint, encoding a two's complement signed 32-bit integer
VarLong ≥ 1
≤ 10
An integer between -9223372036854775808 and 9223372036854775807 Protocol Buffer Varint, encoding a two's complement signed 64-bit integer
Chunk Varies A vertical chunk column See SMP Map Format#Data
Metadata Varies See Entities#Entity Metadata Format
Slot Varies See Slot Data
Object Data 4 or 10 See Object Data
NBT Tag Varies See NBT
Position 8 An integer/block position: x (-33554432 to 33554431), y (-2048 to 2047), z (-33554432 to 33554431) x as a 26-bit integer, followed by y as a 12-bit integer, followed by z as a 26-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 The vanilla Minecraft server internally sends this as two longs.
this.writeLong(uuid.getMostSignificantBits());
this.writeLong(uuid.getLeastSignificantBits());
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.
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.

Position

64-bit value split in to three parts

  • x: 26 MSBs
  • z: 26 LSBs
  • y: 12 bits between them

Encoded as followed:

((x & 0x3FFFFFF) << 38) | ((y & 0xFFF) << 26) | (z & 0x3FFFFFF)

And decoded as:

val = read_unsigned_long();
x = val >> 38;
y = (val >> 26) & 0xFFF;
z = val << 38 >> 38;

Note: The details of bit shifting are rather language dependent; the above may work in Java but probably won't in other languages without some tweaking. In particular, you will usually receive positive numbers even if the actual coordinates are negative. This can be fixed by adding something like the following:

if x >= 2^25 { x -= 2^26 }
if y >= 2^11 { y -= 2^12 }
if z >= 2^25 { z -= 2^26 }

Fixed-point numbers

Some fields may be stored as fixed-point numbers, where a certain number of bits represents the signed integer part (number to the left of the decimal point) and the rest represents the fractional part (to the right). Floating points (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 points, their fractional precision is greater for higher values. This makes them ideal for representing global coordinates of an entity in Minecraft, as it's more important to store the integer part accurately than position them more precisely within a single block (or meter).

Coordinates are often represented as a 32-bit integer, where 5 of the least-significant bits are dedicated to the fractional part, and the rest store the integer part.

Java lacks support for fractional integers directly, but you can represent them as integers. To convert from a double to this integer representation, use the following formulas:

 abs_int = (int)double * 32;

And back again:

 double = (double)abs_int / 32;

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”.

Packet format

Without compression

Field Name Field Type Notes
Length VarInt Length of packet data + length of the packet ID
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 is sent, zlib compression is enabled for all following packets. The format of a packet changes slighty 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)

The length given by the Packet Length field is the number of bytes that remain in that packet, including the Data Length field.

If Data Length is set to zero, then the packet is uncompressed; otherwise it is the size of the uncompressed packet.

If compressed, the uncompressed length of (Packet ID + Data) must be equal to or over the threshold set in the Set Compression packet, otherwise the client/server will disconnect.

Compression can be disabled by sending a Set Compression packet with a Threshold of -1.

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 47)
Server Address String hostname or IP, e.g. localhost or 127.0.0.1
Server Port Unsigned Short default is 25565
Next State VarInt 1 for status, 2 for login

Legacy Server List Ping

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.

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.

Play

Clientbound

Keep Alive

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

Packet ID State Bound To Field Name Field Type Notes
0x00 Play Client Keep Alive ID VarInt

Join Game

See Protocol Encryption for information on logging in.

Packet ID State Bound To Field Name Field Type Notes
0x01 Play Client Entity ID Int The player's Entity ID (EID)
Gamemode Unsigned Byte 0: Survival, 1: Creative, 2: Adventure, 3: Spectator. Bit 3 (0x8) is the hardcore flag.
Dimension Byte -1: Nether, 0: Overworld, 1: End
Difficulty Unsigned Byte 0: peaceful, 1: easy, 2: normal, 3: hard
Max Players Unsigned Byte Used by the client to draw the player list
Level Type String default, flat, largeBiomes, amplified, default_1_1
Reduced Debug Info Boolean If true, a Notchian client shows reduced information on the debug screen.

Warning.png If the Dimension isn't valid then the client will crash

Chat Message

Identifying the difference between Chat/System Message is important as it helps respect the user's chat visibility options. While Position 2 accepts json formatting it will not display, old style formatting works

Packet ID State Bound To Field Name Field Type Notes
0x02 Play Client JSON Data Chat Limited to 32767 bytes
Position Byte 0: chat (chat box), 1: system message (chat box), 2: above action bar

Warning.png Malformed JSON will disconnect the client

Time Update

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
0x03 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

Entity Equipment

Packet ID State Bound To Field Name Field Type Notes
0x04 Play Client Entity ID VarInt Entity's EID
Slot Short Equipment slot. 0: held, 1–4: armor slot (1: boots, 2: leggings, 3: chestplate, 4: helmet)
Item Slot Item in slot format

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
0x05 Play Client Location Position Spawn location

Update Health

Sent by the server to update/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
0x06 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

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
0x07 Play Client Dimension Int -1: The Nether, 0: The Overworld, 1: The End
Difficulty Unsigned Byte 0: Peaceful, 1: Easy, 2: Normal, 3: Hard
Gamemode Unsigned Byte 0: survival, 1: creative, 2: adventure. The hardcore flag is not included
Level Type String Same as Join Game

Warning.png If the Dimension isn't valid then the client will crash

Warning.png Avoid changing player's dimension to same dimension they were already in, weird bugs can occur i.e. such player will be unable to attack other players in new world (fixes after their death and respawn)

Player Position And Look

Updates the player's position on the server.

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.

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

l = x-x0
w = z-z0
c = sqrt( l*l + w*w )
alpha1 = -arcsin(l/c)/PI*180
alpha2 =  arccos(w/c)/PI*180
if alpha2 > 90 then
    yaw = 180 - alpha1
else
    yaw = alpha1

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
0x08 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

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

Held Item Change

Sent to change the player's slot selection.

Packet ID State Bound To Field Name Field Type Notes
0x09 Play Client Slot Byte The slot which the player has selected (0–8)

Use Bed

This packet tells that a player goes to bed.

The client with the matching Entity ID will go into bed mode.

This Packet is sent to all nearby players including the one sent to bed.

Packet ID State Bound To Field Name Field Type Notes
0x0A Play Client Entity ID VarInt Sleeping player's EID
Location Position Block location of the head part of the bed

Animation

Sent whenever an entity should change animation.

Packet ID State Bound To Field Name Field Type Notes
0x0B 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 arm
1 Take damage
2 Leave bed
3 Eat food
4 Critical effect
5 Magic critical effect

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 List Item (Play, 0x38, clientbound) packet that adds the player data for the client to use when spawning a player. If the tab list entry for the UUID included in this packet is not present when this packet arrives, the entity will not be spawned. The tab includes skin/cape data.

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

When in online-mode the UUIDs must be valid and have valid skin blobs, in offline-mode UUID v3 is used.

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.

Packet ID State Bound To Field Name Field Type Notes
0x0C Play Client Entity ID VarInt Player's EID
Player UUID UUID
X Int Player X as a Fixed-Point number
Y Int Player Y as a Fixed-Point number
Z Int Player Z as a Fixed-Point number
Yaw Angle
Pitch Angle
Current Item Short The item the player is currently holding. Note that this should be 0 for “no item”, unlike -1 used in other packets.
Metadata Metadata

Warning.png A negative Current Item crashes clients

Warning.png The client will crash if no Metadata is sent

Collect 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 Player Position (and Player Position And Look) packet sent by the client.

Packet ID State Bound To Field Name Field Type Notes
0x0D Play Client Collected Entity ID VarInt
Collector Entity ID VarInt

Spawn Object

Sent by the server when an Object/Vehicle is created.

Packet ID State Bound To Field Name Field Type Notes
0x0E Play Client Entity ID VarInt EID of the object
Type Byte The type of object (See Objects)
X Int X position as a Fixed-Point number
Y Int Y position as a Fixed-Point number
Z Int Z position as a Fixed-Point number
Pitch Angle
Yaw Angle
Data Object Data

Spawn Mob

Sent by the server when a Mob Entity is Spawned

Packet ID State Bound To Field Name Field Type Notes
0x0F Play Client Entity ID VarInt
Type Unsigned Byte The type of mob. See Mobs
X Int X position as a Fixed-Point number
Y Int Y position as a Fixed-Point number
Z Int Z position as a Fixed-Point number
Yaw Angle
Pitch Angle
Head Pitch Angle
Velocity X Short Same units as Entity Velocity
Velocity Y Short Same units as Entity Velocity
Velocity Z Short Same units as Entity Velocity
Metadata Metadata

Spawn Painting

This packet shows location, name, and type of painting.

Calculating the center of an image: given a (width x height) grid of cells, with (0, 0) being the top left corner, the center is (max(0, width / 2 - 1), height / 2). E.g.

2x1 (1, 0)
4x4 (1, 2)
Packet ID State Bound To Field Name Field Type Notes
0x10 Play Client Entity ID VarInt
Title String Name of the painting. Max length 13
Location Position Center coordinates
Direction Unsigned Byte Direction the painting faces. 0: north (-z), 1: west (-x), 2: south (+z), 3: east (+x)

Spawn Experience Orb

Spawns one or more experience orbs.

Packet ID State Bound To Field Name Field Type Notes
0x11 Play Client Entity ID VarInt Entity's ID
X Int X position as a Fixed-Point number
Y Int Y position as a Fixed-Point number
Z Int Z position as a Fixed-Point number
Count Short The amount of experience this orb will reward once collected

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
0x12 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

Destroy Entities

Sent by the server when a list of entities is to be destroyed on the client.

Packet ID State Bound To Field Name Field Type Notes
0x13 Play Client Count VarInt Number of elements in the following array
Entity IDs Array of VarInt The list of entities of destroy

Entity

This packet may be used to initialize an entity.

For player entities, either this packet or any move/look packet is sent every game tick. So the meaning of this packet is basically that the entity did not move/look since the last such packet.

Packet ID State Bound To Field Name Field Type Notes
0x14 Play Client Entity ID VarInt

Entity Relative Move

This packet is sent by the server when an entity moves less then 4 blocks; if an entity moves more than 4 blocks Entity Teleport should be sent instead.

This packet allows at most four blocks movement in any direction, because byte range is from -128 to 127.

Packet ID State Bound To Field Name Field Type Notes
0x15 Play Client Entity ID VarInt
Delta X Byte Change in X position as a Fixed-Point number
Delta Y Byte Change in Y position as a Fixed-Point number
Delta Z Byte Change in Z position as a Fixed-Point number
On Ground Boolean

Entity Look

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

Packet ID State Bound To Field Name Field Type Notes
0x16 Play Client Entity ID VarInt
Yaw Angle New angle, not a delta
Pitch Angle New angle, not a delta
On Ground Boolean

Entity Look And Relative Move

This packet is sent by the server when an entity rotates and moves. Since a byte range is limited from -128 to 127, and movement is offset of fixed-point numbers, this packet allows at most four blocks movement in any direction. (-128/32 == -4)

Packet ID State Bound To Field Name Field Type Notes
0x17 Play Client Entity ID VarInt
Delta X Byte Change in X position as a Fixed-Point number
Delta Y Byte Change in Y position as a Fixed-Point number
Delta Z Byte Change in Z position as a Fixed-Point number
Yaw Angle New angle, not a delta
Pitch Angle New angle, not a delta
On Ground Boolean

Entity Teleport

This packet is sent by the server when an entity moves more than 4 blocks.

Packet ID State Bound To Field Name Field Type Notes
0x18 Play Client Entity ID VarInt
X Int X position as a Fixed-Point number
Y Int Y position as a Fixed-Point number
Z Int Z position as a Fixed-Point number
Yaw Angle New angle, not a delta
Pitch Angle New angle, not a delta
On Ground Boolean

Entity Head Look

Changes the direction an entity's head is facing.

Packet ID State Bound To Field Name Field Type Notes
0x19 Play Client Entity ID VarInt
Head Yaw Angle New angle, not a delta

Entity Status

Packet ID State Bound To Field Name Field Type Notes
0x1A Play Client Entity ID Int
Entity Status Byte See below
Entity Status Meaning
1 Sent when resetting a mob spawn minecart's timer - appears to be unused by the client
2 Living Entity hurt
3 Living Entity dead
4 Iron Golem throwing up arms
6 Wolf/Ocelot/Horse taming — Spawn “heart” particles
7 Wolf/Ocelot/Horse tamed — Spawn “smoke” particles
8 Wolf shaking water — Trigger the shaking animation
9 (of self) Eating accepted by server
10 Sheep eating grass
10 Play TNT ignite sound
11 Iron Golem handing over a rose
12 Villager mating — Spawn “heart” particles
13 Spawn particles indicating that a villager is angry and seeking revenge
14 Spawn happy particles near a villager
15 Witch animation — Spawn “magic” particles
16 Play zombie converting into a villager sound
17 Firework exploding
18 Animal in love (ready to mate) — Spawn “heart” particles
19 Reset squid rotation
20 Spawn explosion particle — works for some living entities
21 Play guardian sound — works for every entity
22 Enables reduced debug for players
23 Disables reduced debug for players

Attach Entity

This packet is sent when a player has been attached to an entity (e.g. Minecart).

Packet ID State Bound To Field Name Field Type Notes
0x1B Play Client Entity ID Int Attached entity's EID. Set to -1 to detach.
Vehicle ID Int Vechicle's Entity ID
Leash Boolean If true leashes the entity to the vehicle

Entity Metadata

Packet ID State Bound To Field Name Field Type Notes
0x1C Play Client Entity ID VarInt
Metadata Metadata

Entity Effect

Packet ID State Bound To Field Name Field Type Notes
0x1D Play Client Entity ID VarInt
Effect ID Byte See this table
Amplifier Byte Notchian client displays effect level as Amplifier + 1
Duration VarInt Seconds
Hide Particles Boolean

Remove Entity Effect

Packet ID State Bound To Field Name Field Type Notes
0x1E Play Client Entity ID VarInt
Effect ID Byte See this table

Set Experience

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

Packet ID State Bound To Field Name Field Type Notes
0x1F 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

Entity Properties

Packet ID State Bound To Field Name Field Type Notes
0x20 Play Client Entity ID VarInt
Number Of Properties Int Number of elements in the following array
Property Key Array String 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

Known Key values:

Key Default Min Max Label
generic.maxHealth 20.0 0.0 Double.MaxValue Max Health
generic.followRange 32.0 0.0 2048.0 Follow Range
generic.knockbackResistance 0.0 0.0 1.0 Knockback Resistance
generic.movementSpeed 0.699999988079071 0.0 Double.MaxValue Movement Speed
generic.attackDamage 2.0 0.0 Double.MaxValue
horse.jumpStrength 0.7 0.0 2.0 Jump Strength
zombie.spawnReinforcements 0.0 0.0 1.0 Spawn Reinforcements Chance

Modifier Data structure:

Field Name Field Type Notes
UUID UUID
Amount Double
Operation Byte

Chunk Data

Chunks are not unloaded by the client automatically. To unload chunks, send this packet with Ground-Up Continuous=true and no 16^3 chunks (eg. Primary Bit Mask=0). The server does not send skylight information for nether-chunks, it's up to the client to know if the player is currently in the nether. You can also infer this information from the primary bitmask and the amount of uncompressed bytes sent.

See also: SMP Map Format

Changes in 1.8:

  • Data value section removed
  • Extended id section removed
  • Block id section is now a unsigned short (little endian) per a block
  • The block id is equal to (id << 4) | data
Packet ID State Bound To Field Name Field Type Notes
0x21 Play Client Chunk X Int Chunk X coordinate
Chunk Z Int Chunk Z coordinate
Ground-Up Continuous Boolean This is true if the packet represents all sections in this vertical column, where the Primary Bit Mask specifies exactly which sections are included, and which are air
Primary Bit Mask Unsigned Short Bitmask with 1 for every 16x16x16 section whose data follows in the compressed data
Size VarInt Size of Data
Data Chunk

Multi Block Change

Fired whenever 2 or more blocks are changed within the render distance.

Packet ID State Bound To Field Name Field Type Notes
0x22 Play Client Chunk X Int Chunk X coordinate
Chunk Z Int Chunk Z coordinate
Record Count VarInt Number of elements in the following array, a.k.a. the number of blocks affected
Record Horizontal Position Array Unsigned Byte The 4 most significant bits (0xF0) encode the X coordinate, relative to the chunk. The 4 least significant bits (0x0F) encode the Z coordinate, relative to the chunk.
Y Coordinate Unsigned Byte
Block ID VarInt The new block ID for the block. id << 4 | data

Block Change

Fired whenever a block is changed within the render distance.

Packet ID State Bound To Field Name Field Type Notes
0x23 Play Client Location Position Block Coordinates
Block ID VarInt The new block ID for the block. id << 4 | data

Block Action

This packet is used for a number of things:

  • Chests opening and closing
  • Pistons pushing and pulling
  • Note blocks playing
  • Updating beacons

See Also: Block Actions

Packet ID State Bound To Field Name Field Type Notes
0x24 Play Client Location Position Block Coordinates
Byte 1 Unsigned Byte Varies depending on block — see Block Actions
Byte 2 Unsigned Byte Varies depending on block — see Block Actions
Block Type VarInt The block type for the block

Block Break Animation

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

You can also set an animation to air! The animation will still be visible.

If you need to display several break animations at the same time you have to give each of them a unique Entity ID.

Also if you set the coordinates to a special block like water etc. it won't show the actual break animation but some other interesting effects. (Water will lose it's transparency)

Packet ID State Bound To Field Name Field Type Notes
0x25 Play Client Entity ID VarInt EID for the animation
Location Position Block Position
Destroy Stage Byte 0–9 to set it, any other value to remove it

Map Chunk Bulk

1.8 changes at Chunk Data

To reduce the number of bytes, this packet is used to send chunks together for better compression results.

Packet ID State Bound To Field Name Field Type Notes
0x26 Play Client Sky Light Sent Boolean Whether or not Chunk Data contains light nibble arrays. This is true in the Overworld, false in the End + Nether
Chunk Column Count VarInt Number of elements in each of the following arrays
Chunk Meta Chunk X Array Int The X coordinate of the chunk
Chunk Z Int The Z coordinate of the chunk
Primary Bit Mask Unsigned Short A bit mask which specifies which sections are not empty in this chunk
Chunk Data Array of Chunk Each chunk in this array corresponds to the data at the same position in Chunk Meta

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
0x27 Play Client X Float
Y Float
Z Float
Radius Float Currently unused in the client
Record Count Int Number of elements in the following array
Records Array of (Byte, Byte, Byte) Each record is 3 signed bytes long, each bytes are the XYZ (respectively) 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

Effect

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 1013 (mob.wither.spawn), and is ignored for any other value by the client.

Packet ID State Bound To Field Name Field Type Notes
0x28 Play Client Effect ID Int The ID of the effect, see below
Location Position The location of the effect
Data Int Extra data for certain effects, see below
Disable Relative Volume Boolean See above

Effect IDs:

ID Name Data
Sound
1000 random.click
1001 random.click
1002 random.bow
1003 random.door_open or random.door_close (50/50 chance)
1004 random.fizz
1005 Play a music disc. Record ID
1006 not assigned
1007 mob.ghast.charge
1008 mob.ghast.fireball
1009 mob.ghast.fireball, but with a lower volume
1010 mob.zombie.wood
1011 mob.zombie.metal
1012 mob.zombie.woodbreak
1013 mob.wither.spawn
1014 mob.wither.shoot
1015 mob.bat.takeoff
1016 mob.zombie.infect
1017 mob.zombie.unfect
1018 mob.enderdragon.end
1020 random.anvil_break
1021 random.anvil_use
1022 random.anvil_land
Particle
2000 Spawns 10 smoke particles, e.g. from a fire Direction, see below
2001 Block break Block ID
2002 Splash potion. Particle effect + glass break sound. Potion ID
2003 Eye of Ender entity break animation — particles and sound
2004 Mob spawn particle effect: smoke + flames
2005 Spawn “happy villager” effect (green crosses), used for bonemealing vegetation

Smoke directions:

ID Direction
0 South-East
1 South
2 South-West
3 East
4 (Up or middle ?)
5 West
6 North-East
7 North
8 North-West

Sound Effect

Used to play a sound effect on the client.

Custom sounds may be added by resource packs.

Packet ID State Bound To Field Name Field Type Notes
0x29 Play Client Sound name String All known sound effect names can be seen here
Effect position X Int Effect X multiplied by 8
Effect position Y Int Effect Y multiplied by 8
Effect position Z Int Effect Z multiplied by 8
Volume Float 1 is 100%, can be more
Pitch Unsigned Byte 63 is 100%, can be more

Particle

Displays the named particle

Packet ID State Bound To Field Name Field Type Notes
0x2A Play Client Particle ID Int See below
Long Distance Boolean If true, particle distance increases from 256 to 65536
X Float X position of the particle
Y Float Y position of the particle
Z Float 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()
Particle Data Float The data of each particle
Particle Count Int The number of particles to create
Data Array of VarInt Length depends on particle. "iconcrack" has length of 2, "blockcrack", and "blockdust" have lengths of 1, the rest have 0.

Particle IDs:

Particle Name Particle ID
explode 0
largeexplosion 1
hugeexplosion 2
fireworksSpark 3
bubble 4
splash 5
wake 6
suspended 7
depthsuspend 8
crit 9
magicCrit 10
smoke 11
largesmoke 12
spell 13
instantSpell 14
mobSpell 15
mobSpellAmbient 16
witchMagic 17
dripWater 18
dripLava 19
angryVillager 20
happyVillager 21
townaura 22
note 23
portal 24
enchantmenttable 25
flame 26
lava 27
footstep 28
cloud 29
reddust 30
snowballpoof 31
snowshovel 32
slime 33
heart 34
barrier 35
iconcrack_(id)_(data) 36
blockcrack_(id+(data<<12)) 37
blockdust_(id) 38
droplet 39
take 40
mobappearance 41

Change Game State

It appears when a bed can't be used as a spawn point and when the rain state changes.

Packet ID State Bound To Field Name Field Type Notes
0x2B Play Client Reason Unsigned Byte See below
Value Float Depends on Reason

Reason codes:

Reason Effect Value
0 Invalid Bed
1 End raining
2 Begin raining
3 Change game mode 0: Survival, 1: Creative, 2: Adventure, 3: Spectator
4 Enter credits
5 Demo message 0: Show welcome to demo screen, 101: Tell movement controls, 102: Tell jump control, 103: Tell inventory control
6 Arrow hitting player Appears to be played when an arrow strikes another player in Multiplayer
7 Fade value The current darkness value. 1 = Dark, 0 = Bright, Setting the value higher causes the game to change color and freeze
8 Fade time Time in ticks for the sky to fade
10 Play mob appearance (effect and sound) Unknown

Spawn Global Entity

With this packet, the server notifies the client of thunderbolts striking within a 512 block radius around the player. The coordinates specify where exactly the thunderbolt strikes.

Packet ID State Bound To Field Name Field Type Notes
0x2C Play Client Entity ID VarInt The EID of the thunderbolt
Type Byte The global entity type, currently always 1 for thunderbolt
X Int Thunderbolt X, a fixed-point number
Y Int Thunderbolt Y, a fixed-point number
Z Int Thunderbolt Z, a fixed-point number

Open Window

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.

Packet ID State Bound To Field Name Field Type Notes
0x2D Play Client Window ID Unsigned Byte A unique id number for the window to be displayed. Notchian server implementation is a counter, starting at 1.
Window Type String The window type to use for display. See below
Window Title Chat The title of the window
Number Of Slots Unsigned Byte Number of slots in the window (excluding the number of slots in the player inventory)
Entity ID Optional Int EntityHorse's EID. Only sent when Window Type is “EntityHorse”

See inventory windows for further information.

Close Window

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.

Note, notchian clients send a close window packet with Window ID 0 to close their inventory even though there is never an Open Window packet for inventory.

Packet ID State Bound To Field Name Field Type Notes
0x2E Play Client Window ID Unsigned Byte This is the ID of the window that was closed. 0 for inventory.

Set 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
0x2F 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).
Slot Short The slot that should be updated
Slot Data Slot

Window Items

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.

Packet ID State Bound To Field Name Field Type Notes
0x30 Play Client Window ID Unsigned Byte The ID of window which items are being sent for. 0 for player inventory.
Count Short Number of elements in the following array
Slot Data Array of Slot

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

Window 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
0x31 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: Progress arrow 0–200 (presumably in in-game ticks)
1: Fire icon (fuel) 0–200 (presumably in in-game ticks)
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 seed for generating the enchantments view for the client Unknown
4: tooltip shown on mouse hover over top enchantment slot Unknown (set to -1 to hide it)
5: tooltip shown on mouse hover over middle enchantment slot
6: tooltip shown on mouse hover over bottom enchantment slot
Beacon 0: Power level Unknown
1: First potion effect Unknown
2: Second potion effect Unknown
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

Confirm Transaction

A packet from the server indicating whether a request from the client was accepted, or whether there was a conflict (due to lag).

Packet ID State Bound To Field Name Field Type Notes
0x32 Play Client Window ID Byte The ID of the window that the action occurred in
Action Number Short Every action that is to be accepted has a unique number. This field corresponds to that number.
Accepted Boolean Whether the action was accepted

Update Sign

This message is sent from the server to the client whenever a sign is discovered or created. This message is NOT sent when a sign is destroyed or unloaded.

Packet ID State Bound To Field Name Field Type Notes
0x33 Play Client Location Position
Line 1 Chat First line of text in the sign
Line 2 Chat Second line of text in the sign
Line 3 Chat Third line of text in the sign
Line 4 Chat Fourth line of text in the sign

Map

Updates a rectangular area on a map.

Packet ID State Bound To Field Name Field Type Notes
0x34 Play Client Item Damage VarInt The damage value (map ID) of the map being modified
Scale Byte
Icon Count VarInt Number of elements in the following array
Icon Direction And Type Array Byte 0xF0 = Direction, 0x0F = Type
X Byte
Z Byte
Columns Byte Number of columns updated
Rows Optional 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

Update Block Entity

Essentially a block update on a block entity.

Packet ID State Bound To Field Name Field Type Notes
0x35 Play Client Location Position
Action Unsigned Byte The type of update to perform, see below
NBT Data Optional NBT Tag If not present then it's a TAG_END (0)

Action field:

  • 1: Set SpawnPotentials of a mob spawner
  • 2: Set command block text (command and last execution status)
  • 3: Set the level, primary, and secondary powers of a beacon
  • 4: Set rotation and skin of mob head
  • 5: Set type of flower in flower pot
  • 6: Set base color and patterns on a banner

Open Sign Editor

Sent on placement of sign.

Packet ID State Bound To Field Name Field Type Notes
0x36 Play Client Location Position

Statistics

Packet ID State Bound To Field Name Field Type Notes
0x37 Play Client Count VarInt Number of elements in the following array
Statistic Name Array String https://gist.github.com/thinkofdeath/a1842c21a0cf2e1fb5e0
Value VarInt The amount to set it to

Player List Item

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

Packet ID State Bound To Field Name Field Type Notes
0x38 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
Number Of Properties VarInt Number of elements in the following array
Property Name Array String
Value String
Is Signed Boolean
Signature Optional String Only if Is Signed is true
Gamemode VarInt
Ping VarInt
Has Display Name Boolean
Display Name Optional Chat Only if Has Display Name is true
1: update gamemode Gamemode VarInt
2: update latency Ping VarInt
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

Player Abilities

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

The flags are whether damage is disabled (god mode, 8, bit 3), whether the player can fly (4, bit 2), whether the player is flying (2, bit 1), and whether the player is in creative mode (1, bit 0).

To get the values of these booleans, simply AND (&) the byte with 1,2,4 and 8 respectively, to get the 0 or 1 bitwise value. To set them OR (|) them with their repspective masks.

Packet ID State Bound To Field Name Field Type Notes
0x39 Play Client Flags Byte Bit mask, see above
Flying Speed Float
Walking Speed Float

Tab-Complete

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.

Packet ID State Bound To Field Name Field Type Notes
0x3A Play Client Count VarInt Number of elements in the following array
Matches Array of String One eligible command, note that each command is sent separately instead of in a single string, hence the need for Count

Scoreboard Objective

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
0x3B Play Client Objective Name String An 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 String Only if mode is 0 or 2. The text to be displayed for the score
Type Optional String Only if mode is 0 or 2. “integer” or “hearts”

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
0x3C Play Client Score Name String The name of the score to be updated or removed
Action Byte 0 to create/update an item. 1 to remove an item.
Objective Name String 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.

Display Scoreboard

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

Packet ID State Bound To Field Name Field Type Notes
0x3D Play Client Position Byte The position of the scoreboard. 0: list, 1: sidebar, 2: below name.
Score Name String The unique name for the scoreboard to be displayed.

Teams

Creates and updates teams.

Packet ID State Bound To Field Name Field Type Notes
0x3E Play Client Team Name String A unique name for the team. (Shared with scoreboard).
Mode Byte If 0 then the team is created.

If 1 then the team is removed.

If 2 the team team information is updated.

If 3 then new players are added to the team.

If 4 then players are removed from the team.

Team Display Name Optional String Only if Mode = 0 or 2.
Team Prefix Optional String Only if Mode = 0 or 2. Displayed before the players' name that are part of this team
Team Suffix Optional String Only if Mode = 0 or 2. Displayed after the players' name that are part of this team
Friendly Fire Optional Byte Only if Mode = 0 or 2. 0 for off, 1 for on, 3 for seeing friendly invisibles
Name Tag Visibility Optional String Only if Mode = 0 or 2. always, hideForOtherTeams, hideForOwnTeam, never
Color Optional Byte Only if Mode = 0 or 2. Same as Chat colors
Player Count Optional VarInt Only if Mode = 0 or 3 or 4. Number of players in the array
Players Optional Array of String Only if Mode = 0 or 3 or 4. Players to be added/remove from the team. Max 40 characters so may be uuid's later

Plugin Message

Mods and plugins can use this to send their data. Minecraft itself uses a number of plugin channels. These internal channels are prefixed with MC|.

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

Packet ID State Bound To Field Name Field Type Notes
0x3F Play Client Channel String Name of the plugin channel used to send the data
Data Byte Array Any data, depending on the channel. MC| channels are documented here.

Disconnect

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

Packet ID State Bound To Field Name Field Type Notes
0x40 Play Client Reason Chat Displayed to the client when the connection terminates.

Server Difficulty

Changes the difficulty setting in the client's option menu

Packet ID State Bound To Field Name Field Type Notes
0x41 Play Client Difficulty Unsigned Byte 0: peaceful, 1: easy, 2: normal, 3: hard

Combat Event

Packet ID State Bound To Field Name Field Type Notes
0x42 Play Client Event VarInt 0: enter combat, 1: end combat, 2: entity dead
Duration Optional VarInt Only for end combat
Player ID Optional VarInt Only for entity dead
Entity ID Optional Int Only for end combat and entity dead
Message String Only for entity dead

Camera

Packet ID State Bound To Field Name Field Type Notes
0x43 Play Client Camera ID VarInt

World Border

Packet ID State Bound To Field Name Field Type Notes
0x44 Play Client Action VarInt Determines the format of the rest of the packet
Action Field Name
0: set size Radius Double meters
1: lerp size Old Radius Double meters
New Radius Double meters
Speed VarLong number of real-time ticks/seconds (?) until New Radius is reached. From experiments, it appears that Notchian server does not sync world border speed to game ticks, so it gets out of sync with server lag
2: set center X Double
Z Double
3: initialize X Double
Z Double
Old Radius Double
New Radius Double
Speed VarLong
Portal Teleport Boundary VarInt Resulting coordinates from a portal teleport are limited to +-value. Usually 29999984.
Warning Time VarInt
Warning Blocks VarInt
4: set warning time Warning Time VarInt unit?
5: set warning blocks Warning Blocks VarInt

Title

Packet ID State Bound To Field Name Field Type Notes
0x45 Play Client Action VarInt
Action Field Name
0: set title Title Text Chat
1: set subtitle Subtitle Text Chat
2: set times and display Fade In Int ticks
Stay Int ticks
Fade Out Int ticks
3: hide no fields no fields
4: reset no fields no fields

“Hide” makes the title disappear, but if you run times again the same title will appear. “Reset” erases the text.

Set Compression

Packet ID State Bound To Field Name Field Type Notes
0x46 Play Client Threshold VarInt Packets of this size or higher may be compressed

Player List Header/Footer

Packet ID State Bound To Field Name Field Type Notes
0x47 Play Client Header Chat
Footer Chat

Resource Pack Send

Packet ID State Bound To Field Name Field Type Notes
0x48 Play Client URL String The URL to the resource pack.
Hash String A 40 character hexadecimal and lowercase SHA-1 hash of the resource pack file. (must be lower case in order to work)
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

Update Entity NBT

Packet ID State Bound To Field Name Field Type Notes
0x49 Play Client Entity ID VarInt
Tag NBT Tag

Serverbound

Keep Alive

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
0x00 Play Server Keep Alive ID VarInt

Chat Message

The default server will check the message to see if it begins with a '/'. If it doesn't, the username of the sender is prepended and sent to all other clients (including the original sender). If it does, the server assumes it to be a command and attempts to process it. A message longer than 100 characters will cause the server to kick the client. This change was initially done by allowing the client to not slice the message up to 119 (the previous limit), without changes to the server. For this reason, the vanilla server kept the code to cut messages at 119, but this isn't a protocol limitation and can be ignored.

Packet ID State Bound To Field Name Field Type Notes
0x01 Play Server Message String The client sends the raw input, not Chat

Use Entity

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.

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

Packet ID State Bound To Field Name Field Type Notes
0x02 Play Server Target VarInt
Type VarInt 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

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
0x03 Play Server On Ground Boolean True if the client is on the ground, false otherwise

Player Position

Updates the player's XYZ position on the server.

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 units, this will result in the client being kicked for “You moved too quickly :( (Hacking?)”

If the distance is greater than 10 units, the server will log the warning message "<name> moved too quickly!", followed by two coordinate triples (maybe movement delta?), but will not kick the client.

Also if the fixed-point number of X or Z is set greater than 3.2×107 the client will be kicked for “Illegal position”.

Packet ID State Bound To Field Name Field Type Notes
0x04 Play Server X Double Absolute position
Feet Y Double Absolute position, normally Head Y - 1.62
Z Double Absolute position
On Ground Boolean True if the client is on the ground, false otherwise

Player Look

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 of player (in degrees), standing at point (x0, z0) and looking towards point (x, z) one can be calculated with:

l = x-x0
w = z-z0
c = sqrt( l*l + w*w )
alpha1 = -arcsin(l/c)/PI*180
alpha2 =  arccos(w/c)/PI*180
if alpha2 > 90 then
    yaw = 180 - alpha1
else
    yaw = alpha1

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
0x05 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

Player Position And Look

A combination of Player Look and Player Position.

Packet ID State Bound To Field Name Field Type Notes
0x06 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

Player Digging

Sent when the player mines a block. A Notchian server only accepts digging packets with coordinates within a 6-unit radius of the player's position.

Packet ID State Bound To Field Name Field Type Notes
0x07 Play Server Status Byte The action the player is taking against the block (see below)
Location Position Block position
Face Byte The face being hit (see below)

Status can (currently) be one of six values:

Meaning Value
Started digging 0
Cancelled digging 1
Finished digging 2
Drop item stack 3
Drop item 4
Shoot arrow / finish eating 5

Notchian clients send a 0 (started digging) when they start digging and a 2 (finished digging) once they think they are finished. If digging is aborted, the client simply send a 1 (cancel digging).

Status code 4 (drop item) is a special case. In-game, when you use the Drop Item command (keypress 'q'), a dig packet with a status of 4, and all other values set to 0, is sent from client to server. Status code 3 is similar, but drops the entire stack.

Status code 5 (shoot arrow / finish eating) is also a special case. The x, y and z fields are all set to 0 like above, with the exception of the face field, which is set to 255.

The face can be one of six values, representing the face being hit:

Value 0 1 2 3 4 5
Offset -Y +Y -Z +Z -X +X

Player Block Placement

Packet ID State Bound To Field Name Field Type Notes
0x08 Play Server Location Position Block position
Face Byte The face on which the block is placed (see above)
Held Item Slot
Cursor Position X Byte The position of the crosshair on the block
Cursor Position Y Byte
Cursor Position Z Byte

In normal operation (i.e. placing a block), this packet is sent once, with the values set normally.

This packet has a special case where X, Y, Z, and Face are all -1. (Note that Y is unsigned so set to 255.) This special packet indicates that the currently held item for the player should have its state updated such as eating food, pulling back bows, using buckets, etc.

In a Notchian Beta client, the block or item ID corresponds to whatever the client is currently holding, and the client sends one of these packets any time a right-click is issued on a surface, so no assumptions can be made about the safety of the ID. However, with the implementation of server-side inventory, a Notchian server seems to ignore the item ID, instead operating on server-side inventory information and holding selection. The client has been observed (1.2.5 and 1.3.2) to send both real item IDs and -1 in a single session.

Special note on using buckets: When using buckets, the Notchian client might send two packets: first a normal and then a special case. The first normal packet is sent when you're looking at a block (e.g. the water you want to scoop up). This normal packet does not appear to do anything with a Notchian server. The second, special case packet appears to perform the action — based on current position/orientation and with a distance check — it appears that buckets can only be used within a radius of 6 units.

Held Item Change

Sent when the player changes the slot selection

Packet ID State Bound To Field Name Field Type Notes
0x09 Play Server Slot Short The slot which the player has selected (0–8)

Animation

Sent when the player's arm swings

Packet ID State Bound To Field Name Field Type Notes
0x0A Play Server no fields

Entity Action

Sent at least when crouching, leaving a bed, or sprinting. To send action animation to client use 0x28. The client will send this with Action ID = 3 when “Leave Bed” is clicked.

Packet ID State Bound To Field Name Field Type Notes
0x0B Play Server Entity ID VarInt Player ID
Action ID VarInt The ID of the action, see below
Jump Boost VarInt Horse jump boost. Ranged from 0 -> 100.

Action ID can be one of the following values:

ID Action
0 Crouch
1 Uncrouch
2 Leave bed
3 Start sprinting
4 Stop sprinting
5 Jump with horse
6 Open inventory

Steer Vehicle

Packet ID State Bound To Field Name Field Type Notes
0x0C Play Server Sideways Float Positive to the left of the player
Forward Float Positive forward
Flags Unsigned Byte Bit mask. 0x1: jump, 0x2: unmount

Close Window

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

Note, Notchian clients send a close window message with Window ID 0 to close their inventory even though there is never an Open Window message for inventory.

Packet ID State Bound To Field Name Field Type Notes
0x0D Play Server Window ID Unsigned Byte This is the ID of the window that was closed. 0 for inventory.

Click Window

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

Packet ID State Bound To Field Name Field Type Notes
0x0E Play Server Window ID Unsigned Byte The ID of the window which was clicked. 0 for player inventory.
Slot Short The clicked slot Nr., see below
Button Byte The button used in the click, see below
Action Number Short A unique number for the action, implemented by Notchian as a counter, starting at 1. Used by the server to send back a Confirm Transaction.
Mode Byte Inventory operation mode, see below
Clicked item Slot The clicked slot. Has to be empty (item ID = -1) for drop mode.

See inventory windows 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
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
3 2 Normal Middle click
4 0 Normal* Drop key (Q) (* Clicked item is different, see above)
1 Normal* Ctrl + Drop key (Ctrl-Q) (drops full stack)
0 -999 Left click outside inventory holding nothing (no-op)
1 -999 Right click outside inventory holding nothing (no-op)
5 0 -999 Starting left mouse drag (or middle mouse)
4 -999 Starting right mouse drag
1 Normal Add slot for left-mouse drag
5 Normal Add slot for right-mouse drag
2 -999 Ending left mouse drag
6 -999 Ending right mouse drag
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.

The server will send back a Confirm Transaction packet. If the click was not accepted, the client must reflect that packet before sending more Click Window packets, otherwise the server will reject them silently. The Notchian server also sends a Window Items packet for the open window and Set Slot packets for the clicked and cursor slot, but only when the click was not accepted, probably to resynchronize client and server.

Confirm Transaction

<SpaceManiac> noooo idea why the serverbound confirm transaction packet exists
<SpaceManiac> I think it's sent as a response to the clientbound confirm transaction in some situations, but it's fuzzy
Packet ID State Bound To Field Name Field Type Notes
0x0F Play Server Window ID Byte The ID of the window that the action occurred in
Action Number Short Every action that is to be accepted has a unique number. This field corresponds to that number.
Accepted Boolean Whether the action was accepted

Creative Inventory Action

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
0x10 Play Server Slot Short Inventory slot
Clicked Item Slot

Enchant Item

Packet ID State Bound To Field Name Field Type Notes
0x11 Play Server Window ID Byte The ID of the enchantment table window sent by Open Window
Enchantment Byte The position of the enchantment on the enchantment table window, starting with 0 as the topmost one

Update Sign

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

Packet ID State Bound To Field Name Field Type Notes
0x12 Play Server Location Position Block Coordinates
Line 1 Chat First line of text in the sign
Line 2 Chat Second line of text in the sign
Line 3 Chat Third line of text in the sign
Line 4 Chat Fourth line of text in the sign

Player Abilities

The latter 2 bytes are used to indicate the walking and flying speeds respectively, while the first byte is used to determine the value of 4 booleans.

The vanilla client sends this packet when the player starts/stops flying with the second parameter changed accordingly. All other parameters are ignored by the vanilla server.

Packet ID State Bound To Field Name Field Type Notes
0x13 Play Server Flags Byte Bit mask. 0x08: damage disabled (god mode), 0x04: can fly, 0x02: is flying, 0x01: is Creative
Flying Speed Float
Walking Speed Float

Tab-Complete

Sent when the user presses tab while writing text.

Packet ID State Bound To Field Name Field Type Notes
0x14 Play Server Text String All text behind the cursor
Has Position Boolean
Looked At Block Optional Position The position of the block being looked at. Only sent if Has Position is true

Client Settings

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

Packet ID State Bound To Field Name Field Type Notes
0x15 Play Server Locale String e.g. en_GB
View Distance Byte Client-side render distance, in chunks
Chat Mode Byte 0: enabled, 1: commands only, 2: hidden
Chat Colors Boolean “Colors” multiplayer setting
Displayed Skin Parts Unsigned Byte Skin parts, see note below

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.

Client Status

Sent when the client is ready to complete login and when the client is ready to respawn after death.

Packet ID State Bound To Field Name Field Type Notes
0x16 Play Server Action ID VarInt See below

Action ID values:

Action ID Action
0 Perform respawn
1 Request stats
2 Taking Inventory achievement

Plugin Message

Mods and plugins can use this to send their data. Minecraft itself uses a number of plugin channels. These internal channels are prefixed with MC|.

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

Note that the data length is known from the packet length, so there is no need for a length member being sent.

Packet ID State Bound To Field Name Field Type Notes
0x17 Play Server Channel String Name of the plugin channel used to send the data
Data Byte Array Any data, depending on the channel. MC| channels are documented here.

Spectate

Packet ID State Bound To Field Name Field Type Notes
0x18 Play Server Target Player UUID

Resource Pack Status

Packet ID State Bound To Field Name Field Type Notes
0x19 Play Server Hash String The hash sent in the Resource Pack Send packet.
Result VarInt 0: successfully loaded, 1: declined, 2: failed download, 3: accepted

Status

The status ping works as follows.

C->S : Handshake State=1
C->S : Request
S->C : Response
C->S : Ping
S->C : Pong

Clientbound

Response

Packet ID State Bound To Field Name Field Type Notes
0x00 Status Client JSON Response String See Server List Ping#Response

Pong

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

Request

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

Ping

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: Login Success and Set Compression

Login Success and Set Compression can be sent in either order, but anything after Set Compression must use the Post Compression packet format. The packet ID for Set Compression also depends on the current connection state, and Login Success switches the state to play, meaning that the correct packet ID must be used depending on the order chosen.

For unauthenticated and localhost connections (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.

See Protocol Encryption for details.

Clientbound

Disconnect

Packet ID State Bound To Field Name Field Type Notes
0x00 Login Client Reason Chat

Encryption Request

Packet ID State Bound To Field Name Field Type Notes
0x01 Login Client Server ID String Appears to be empty
Public Key Length VarInt Length of Public Key
Public Key Byte Array
Verify Token Length VarInt Length of Verify Token
Verify Token Byte Array

See Protocol Encryption for details.

Login Success

Packet ID State Bound To Field Name Field Type Notes
0x02 Login Client UUID String Unlike in other packets, this field contains the UUID as a string with hyphens.
Username String

This packet switches the connection state to play.

Set Compression

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

Serverbound

Login Start

Packet ID State Bound To Field Name Field Type Notes
0x00 Login Server Name String

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
Verify Token Length VarInt Length of Verify Token
Verify Token Byte Array

See Protocol Encryption for details.