Protocol

This page presents a dissection of the current stable Minecraft protocol. The current pre-release protocol is documented elsewhere.

Credit goes to the Great Old Ones, and the citizens of #mcdevs who helped by providing packet dumps and insight. If you're having trouble, check out the FAQ. Make sure you check the Data Types page.

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

The protocol for Pocket Minecraft is substantially different, and is documented at Pocket Minecraft Protocol.

Additionally, the minecraft server supports two other protocols since beta 1.9pre4, Rcon (for remote administration) and Query (to query server properties). With the default settings, they listen on TCP 25575 and UDP 25565 respectively.

This is a fairly lengthy page, and to make it more readable certain terminology must be understood. Terms used on this page and their definition are provided below.

	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 in the world. This definition is subject to change as Notch extends the protocol
EID	An EID - or Entity ID - is a unique 4-byte integer used to identify a specific entity
XYZ	In this document, the axis names are the same as those used by Notch. Y points upwards, X points South, and Z points West.

Plugin Channels

Plugin channels (present in 0xFA) are used to supplement the protocol. Information about these channels can be found at their page: plugin channel

Packets

All packets begin with a single "Packet ID" byte. Listed packet size includes this byte. Packets are either "server to client", "client to server", or both. If not specified, assume that the packet can be sent both ways. There is no "length" field; for variable length packets, you must parse to the end to determine the length.

Keep Alive (0x00)

Two-Way

The server will frequently send out a keep-alive, each containing a random ID. The client must respond with the same packet. The Beta server will disconnect a client if it doesn't receive at least one packet before 1200 in-game ticks, and the Beta client will time out the connection under the same conditions. The client may send packets with Keep-alive ID=0.

Packet ID	Field Name	Field Type	Example	Notes
0x00	Keep-alive ID	int	957759560	Server-generated random id
Total Size:	5 bytes

Login Request (0x01)

Server to Client

See Protocol Encryption for information on logging in.

Packet ID	Field Name	Field Type	Example	Notes
0x01	Entity ID	int	1298	The Player's Entity ID
	Level type	string	default	default, flat, or largeBiomes. level-type in server.properties
	Game mode	byte	0	0: survival, 1: creative, 2: adventure. Bit 3 (0x8) is the hardcore flag
	Dimension	byte	0	-1: nether, 0: overworld, 1: end
	Difficulty	byte	1	0 thru 3 for Peaceful, Easy, Normal, Hard
	Not used	byte	0	Only 0 observed from vanilla server, was previously world height
	Max players	byte	8	Used by the client to draw the player list
Total Size:	12 bytes + length of strings

Handshake (0x02)

Client to server

See Protocol Encryption for information on logging in.

Packet ID	Field Name	Field Type	Example	Notes
0x02	Protocol Version	byte	51	As of 1.4.6 the protocol version is 51
	Username	string	_AlexM	The username of the player attempting to connect
	Server Host	string	localhost
	Server Port	int	25565
Total Size:	10 bytes + length of strings

Chat Message (0x03)

Two-Way

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. (As of 1.3.2, the vanilla client appears to limit the text a user can enter to 100 charaters.) This limits the chat message packet length to 103 bytes. Note that this limit does not apply to incoming chat messages as the server may have prepended other information, not limited to, but usually including, a username.

A message longer than 119 characters will cause the server and client to print the message "Received string length longer than maximum allowed (X > 119)", with no side effects.

For more information, see Chat.

Packet ID	Field Name	Field Type	Example	Notes
0x03	Message	string	<Bob> Hello World!	User input must be sanitized server-side
Total Size:	3 bytes + length of strings

Time Update (0x04)

Server to Client

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	Field Name	Field Type	Example	Notes
0x04	Age of the world	long	45464654	In ticks; not changed by server commands
	Time of Day	long	21321	The world (or region) time, in ticks
Total Size:	17 Bytes

Entity Equipment (0x05)

Server to Client

Packet ID	Field Name	Field Type	Example	Notes
0x05	Entity ID	int	0x00010643	Named Entity ID
	Slot	short	4	Equipment slot: 0=held, 1-4=armor slot
	Item	slot		Item in slot format
Total Size:	7 bytes + slot data

Spawn Position (0x06)

Server to Client

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	Field Name	Field Type	Example	Notes
0x06	X	int	117	Spawn X in block coordinates
	Y	int	70	Spawn Y in block coordinates
	Z	int	-46	Spawn Z in block coordinates
Total Size:	13 bytes

Use Entity (0x07)

Client to Server

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.

Packet ID	Field Name	Field Type	Example	Notes
0x07	User	int	1298	The entity of the player (ignored by the server)
	Target	int	1805	The entity the player is interacting with
	Mouse button	boolean	true	true when the player is left-clicking and false when right-clicking.
Total Size:	10 bytes

Update Health (0x08)

Server to Client

Sent by the server to update/set the health of the player it is sent to. Added in protocol version 5.

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	Field Name	Field Type	Example	Notes
0x08	Health	short	20	0 or less = dead, 20 = full HP
	Food	short	20	0 - 20
	Food Saturation	float	5.0	Seems to vary from 0.0 to 5.0 in integer increments
Total Size:	9 bytes

Respawn (0x09)

Server to Client

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	Field Name	Field Type	Example	Notes
0x09	Dimension	int	1	-1: The Nether, 0: The Overworld, 1: The End
	Difficulty	byte	1	0 thru 3 for Peaceful, Easy, Normal, Hard. 1 is always sent c->s
	Game mode	byte	1	0: survival, 1: creative, 2: adventure. The hardcore flag is not included
	World height	short	256	Defaults to 256
	Level type	string	default	See 0x01 login
Total Size:	11 bytes + length of string

Player (0x0A)

Client to Server

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.

This packet was previously referred to as Flying

Packet ID	Field Name	Field Type	Example	Notes
0x0A	On Ground	boolean	1	True if the client is on the ground, False otherwise
Total Size:	2 bytes

Player Position (0x0B)

Client to Server

Updates the players XYZ position on the server. If Stance - Y is less than 0.1 or greater than 1.65, the stance is illegal and the client will be kicked with the message “Illegal Stance”. 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 will result in the client being kicked for "You moved too quickly :( (Hacking?)" Also if the absolute number of X or Z is set greater than 3.2E7D the client will be kicked for "Illegal position"

Packet ID	Field Name	Field Type	Example	Notes
0x0B	X	double	102.809	Absolute position
	Y	double	70.00	Absolute position
	Stance	double	71.62	Used to modify the players bounding box when going up stairs, crouching, etc…
	Z	double	68.30	Absolute position
	On Ground	boolean	1	Derived from packet 0x0A
Total Size:	34 bytes

Player Look (0x0C)

Client to Server

The unit circle for yaw

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 backwards towards (-1, 0), or in other words, it turns clockwise instead of counterclockwise. 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.

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	Field Name	Field Type	Example	Notes
0x0C	Yaw	float	0.00	Absolute rotation on the X Axis, in degrees
	Pitch	float	0.00	Absolute rotation on the Y Axis, in degrees
	On Ground	boolean	1	Derived from packet 0x0A
Total Size:	10 bytes

Player Position and Look (0x0D)

Two-Way

A combination of Player Look and Player position.

Note: When this packet is sent from the server, the 'Y' and 'Stance' fields are swapped.

Packet ID	Field Name	Field Type	Example	Notes
0x0D	X	double	6.5	Absolute position
	Y	double	65.620000004768372	Absolute position
	Stance	double	67.240000009536743	Used to modify the players bounding box when going up stairs, crouching, etc…
	Z	double	7.5	Absolute position
	Yaw	float	0.0	Absolute rotation on the X Axis
	Pitch	float	0.0	Absolute rotation on the Y Axis
	On Ground	boolean	0	Derived from packet 0x0A
Total Size:	42 bytes

Player Digging (0x0E)

Client to Server

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	Field Name	Field Type	Example	Notes
0x0E	Status	byte	1	The action the player is taking against the block (see below)
	X	int	32	Block position
	Y	byte	64	Block position
	Z	int	32	Block position
	Face	byte	3	The face being hit (see below)
Total Size:	12 bytes

Status can (currently) be one of six values:

Meaning	Value
Started digging	0
Cancelled digging	1
Finished digging	2
Check block	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, no notice is sent to the server; the client simply does not send a 2 (finished digging).

Status code 3 is never sent by a Notchian client, but it is supported by Notchian servers. If the block coordinates are within a 16-unit radius of the player's position, the server responds with a Block Change packet containing that block's current type and metadata. No actual changes occur to the world in this case.

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 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

In 1.7.3, when a player opens a door with left click the server receives Packet 0xE+start digging and opens the door.

Player Block Placement (0x0F)

Client to Server

Packet ID	Field Name	Field Type	Example	Notes
0x0F	X	int	32	Block position
	Y	unsigned byte	64	Block position
	Z	int	32	Block position
	Direction	byte	3	The offset to use for block/item placement (see below)
	Held item	slot
	Cursor position X	byte	0 - 16	The position of the crosshair on the block
	Cursor position Y	byte	0 - 16
	Cursor position Z	byte	0 - 16
Total Size:	14 bytes + slot data

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

This packet has a special case where X, Y, Z, and Direction 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, shooting 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 (0x10)

Two-Way

Sent when the player changes the slot selection

Packet ID	Field Name	Field Type	Example	Notes
0x10	Slot ID	short	1	The slot which the player has selected (0-8)
Total Size:	3 bytes

Use Bed (0x11)

Server to Client

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	Field Name	Field Type	Example	Notes
0x11	Entity ID	int	89	Player ID
	Unknown	byte	0	Only 0 has been observed
	X coordinate	int	-247	Bed headboard X as block coordinate
	Y coordinate	byte	78	Bed headboard Y as block coordinate
	Z coordinate	int	128	Bed headboard Z as block coordinate
Total Size:	15 bytes

Animation (0x12)

Two-Way

Sent whenever an entity should change animation.

Packet ID	Field Name	Field Type	Example	Notes
0x12	EID	int	55534	Player ID
	Animation	byte	1	Animation ID
Total Size:	6 bytes

Animation can be one of the following values:

ID	Animation
0	No animation
1	Swing arm
2	Damage animation
3	Leave bed
5	Eat food
102	(unknown)
104	Crouch
105	Uncrouch

Only 1 (swing arm) is sent by notchian clients. Crouching is sent via 0x13. Damage is server-side, and so is not sent by notchian clients. See also 0x26.

Entity Action (0x13)

Client to Server

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	Field Name	Field Type	Example	Notes
0x13	EID	int	55534	Player ID
	Action ID	byte	1	The ID of the action, see below.
Total Size:	6 bytes

Action ID can be one of the following values:

ID	Action
1	Crouch
2	Uncrouch
3	Leave bed
4	Start sprinting
5	Stop sprinting

Spawn Named Entity (0x14)

Server to Client

The only named entities (at the moment) are players (either real or NPC/Bot). This packet is sent by the server when a player comes into visible range, not when a player joins.

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

At one point, the Notchian client was not okay with receiving player entity packets, including 0x14, that refer to its own username or EID; and would teleport to the absolute origin of the map and fall through the Void any time it received them. However, in more recent versions, it appears to handle them correctly, by spawning a new entity as directed (though future packets referring to the entity ID may be handled incorrectly).

Packet ID	Field Name	Field Type	Example	Notes
0x14	EID	int	94453	Player ID
	Player Name	string	Twdtwd	Max length of 16
	X	int	784	Player X as Absolute Integer
	Y	int	2131	Player Y as Absolute Integer
	Z	int	-752	Player Z as Absolute Integer
	Yaw	byte	0	Player rotation as a packed byte
	Pitch	byte	0	Player rotation as a packed byte
	Current Item	short	0	The item the player is currently holding. Note that this should be 0 for "no item", unlike -1 used in other packets. A negative value crashes clients.
	Metadata	Metadata		The 1.3 client crashes on packets with no metadata, but the server can send any metadata key of 0, 1 or 8 and the client is fine.
Total Size:	22 bytes + length of strings + metadata (at least 1)

Collect Item (0x16)

Server to Client

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 (0x1D does that), and it doesn't add it to your inventory (0x68 does that). The server only checks for items to be picked up after each Player Position and Player Position & Look packet sent by the client.

Packet ID	Field Name	Field Type	Example	Notes
0x16	Collected EID	int	38
	Collector EID	int	20
Total Size:	9 bytes

Spawn Object/Vehicle (0x17)

Server to Client

Sent by the server when an Object/Vehicle is created. The throwers entity id is now used for fishing floats too.

Packet ID	Field Name	Field Type	Example	Notes
0x17	EID	int	62	Entity ID of the Object
	Type	byte	11	The type of object (see Entities#Objects)
	X	int	16080	The Absolute Integer X Position of the object
	Y	int	2299	The Absolute Integer Y Position of the object
	Z	int	592	The Absolute Integer Z Position of the object
	Yaw	byte	0	The yaw in steps of 2p/256
	Pitch	byte	67	The pitch in steps of 2p/256
	Object Data			Object Data
	Total Size:	22 or 28 bytes

Spawn Mob (0x18)

Server to Client

Sent by the server when a Mob Entity is Spawned

Packet ID	Field Name	Field Type	Example	Notes
0x18	EID	int	446	Entity ID
	Type	byte	91	The type of mob. See Entities#Mobs
	X	int	13366	The Absolute Integer X Position of the object
	Y	int	2176	The Absolute Integer Y Position of the object
	Z	int	1680	The Absolute Integer Z Position of the object
	Yaw	byte	-27	The yaw in steps of 2p/256
	Pitch	byte	0	The pitch in steps of 2p/256
	Head Yaw	byte		Head yaw in steps of 2p/256
	Velocity Z	short	0
	Velocity X	short	0
	Velocity Y	short	0
	Metadata	Metadata	127	Varies by mob, see Entities
Total Size:	27 bytes + Metadata (at least 1)

Spawn Painting (0x19)

Server to Client

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

Packet ID	Field Name	Field Type	Example	Notes
0x19	Entity ID	int	0x00000326	Unique entity ID
	Title	string	Creepers	Name of the painting; max length 13 (length of "SkullAndRoses")
	X	int	50	Center X coordinate
	Y	int	66	Center Y coordinate
	Z	int	-50	Center Z coordinate
	Direction	int	0	Direction the painting faces (0 -z, 1 -x, 2 +z, 3 +x)
Total Size:	23 bytes + length of string

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)

Spawn Experience Orb (0x1A)

Server to Client

Spawns one or more experience orbs. Coordinates are in absolute units.

Packet ID	Field Name	Field Type	Example	Notes
0x1A	Entity ID	int	105668
	x	int	-1143
	y	int	1952
	z	int	1166
	count	short	7
Total Size:	19 bytes

Entity Velocity (0x1C)

Server to Client

This packet is new to version 4 of the protocol, and is believed to be Entity Velocity/Motion.

Velocity is believed to be in units of 1/32000 of a block per server tick (200ms); for example, -1343 would move (-1343 / 32000) = -0.04196875 blocks per tick (or -0.20984375 blocks per second).

Each axis' velocity is capped between -0.9 and 0.9 blocks per tick (packet values -28800 to 28800).

(This packet data values are not fully verified)

Packet ID	Field Name	Field Type	Example	Notes
0x1C	Entity ID	int	1805	The entity ID
	Velocity X	short	-1343	Velocity on the X axis
	Velocity Y	short	0	Velocity on the Y axis
	Velocity Z	short	0	Velocity on the Z axis
Total Size:	11 bytes

Destroy Entity (0x1D)

Server to Client

Sent by the server when an list of Entities is to be destroyed on the client.

Packet ID	Field Name	Field Type	Example	Notes
0x1D	Entity Count	byte	3	The amount of entities which should be destroyed
	Entity IDs	array of int	452, 546, 123	The list of entity ids which should be destroyed
Total Size:	2 + (entity count * 4) bytes

Entity (0x1E)

Server to Client

Most entity-related packets are subclasses of this packet. When sent from the server to the client, it may initialize the entry.

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	Field Name	Field Type	Example	Notes
0x1E	EID	int	446	Entity ID
Total Size:	5 bytes

Entity Relative Move (0x1F)

Server to Client

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. Movement is an offset of Absolute Int; to convert relative move to block coordinate offset, divide by 32.

Packet ID	Field Name	Field Type	Example	Notes
0x1F	EID	int	459	Entity ID
	dX	byte	1	X axis Relative movement as an Absolute Integer
	dY	byte	-7	Y axis Relative movement as an Absolute Integer
	dZ	byte	5	Z axis Relative movement as an Absolute Integer
Total Size:	8 bytes

Entity Look (0x20)

Server to Client

This packet is sent by the server when an entity rotates. Example: "Yaw" field 64 means a 90 degree turn.

Packet ID	Field Name	Field Type	Example	Notes
0x20	EID	int	459	Entity ID
	Yaw	byte	126	The X Axis rotation as a fraction of 360
	Pitch	byte	0	The Y Axis rotation as a fraction of 360
Total Size:	7 bytes

Entity Look and Relative Move (0x21)

Server to Client

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 Absolute Int, this packet allows at most four blocks movement in any direction. (-128/32 == -4)

Packet ID	Field Name	Field Type	Example	Notes
0x21	EID	int	459	Entity ID
	dX	byte	1	X axis Relative movement as an Absolute Integer
	dY	byte	-7	Y axis Relative movement as an Absolute Integer
	dZ	byte	5	Z axis Relative movement as an Absolute Integer
	Yaw	byte	126	The X Axis rotation as a fraction of 360
	Pitch	byte	0	The Y Axis rotation as a fraction of 360
Total Size:	10 bytes

Entity Teleport (0x22)

Server to Client

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

Packet ID	Field Name	Field Type	Example	Notes
0x22	EID	int	459	Entity ID
	X	int	14162	X axis position as an Absolute Integer
	Y	int	2176	Y axis position as an Absolute Integer
	Z	int	1111	Z axis position as an Absolute Integer
	Yaw	byte	126	The X Axis rotation as a fraction of 360
	Pitch	byte	0	The Y Axis rotation as a fraction of 360
Total Size:	19 bytes

Entity Head Look (0x23)

Server to Client

Changes the direction an entity's head is facing.

Packet ID	Field Name	Field Type	Example	Notes
0x23	Entity ID	int
	Head Yaw	byte		Head yaw in steps of 2p/256
Total Size:	6 bytes

Entity Status (0x26)

Server to Client

Packet ID	Field Name	Field Type	Example	Notes
0x26	Entity ID	Int	34353
	Entity Status	Byte	0x03	See below
	Total Size:	6 bytes

Entity Status	Meaning
2	Entity hurt
3	Entity dead
6	Wolf taming
7	Wolf tamed
8	Wolf shaking water off itself
9	(of self) Eating accepted by server
10	Sheep eating grass

Attach Entity (0x27)

Server to Client

This packet is new to version 4 of the protocol, and is believed to be Attach Entity.

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

(This packet data values are not fully verified)

Packet ID	Field Name	Field Type	Example	Notes
0x27	Entity ID	int	1298	The player entity ID being attached
	Vehicle ID	int	1805	The vehicle entity ID attached to (-1 for unattaching)
Total Size:	9 bytes

Entity Metadata (0x28)

Server to Client

Packet ID	Field Name	Field Type	Example	Notes
0x28	Entity ID	int	0x00000326	Unique entity ID to update.
	Entity Metadata	Metadata	0x00 0x01 0x7F	Metadata varies by entity. See Entities
Total Size:	5 bytes + Metadata

Entity Effect (0x29)

Server to Client

Packet ID	Field Name	Field Type	Example	Notes
0x29	Entity ID	int	14	Entity ID of a player
	Effect ID	byte	17	See here
	Amplifier	byte	0
	Duration	short	64
Total Size:	9 bytes

Remove Entity Effect (0x2A)

Server to Client

Packet ID	Field Name	Field Type	Example	Notes
0x2a	Entity ID	int		Entity ID of a player
	Effect ID	byte	17	See table above
Total Size:	6 bytes

Set Experience (0x2B)

Server to Client

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

Packet ID	Field Name	Field Type	Example	Notes
0x2B	Experience bar	float	0.5960060358047485	Used for drawing the experience bar - value is between 0 and 1.
	Level	short	8
	Total experience	short	130
Total Size:	9 bytes

Chunk Data (0x33)

Server to Client

See also: Map Format

Chunks are sent a column at a time, with some sections optionally missing from each packet (those consisting only of air).

Packet ID	Field Name	Field Type	Example	Notes
0x33	X	int		Chunk X Coordinate (*16 to get true X)
	Z	int		Chunk Z Coordinate (*16 to get true Z)
	Ground-up continuous	boolean		This is True if the packet represents all sections in this vertical column, where the primary bit map specifies exactly which sections are included, and which are air.
	Primary bit map	unsigned short	15	Bitmask with 1 for every 16x16x16 section which data follows in the compressed data.
	Add bit map	unsigned short	0	Same as above, but this is used exclusively for the 'add' portion of the payload
	Compressed size	int		Size of compressed chunk data.
	Compressed data	unsigned byte array	…	The chunk data is compressed using ZLib Deflate function.
Total Size:	18 bytes + Compressed chunk size

The payload is a set of 16x16x16 sections, sharing the same X and Z coordinates. What is and isn't sent is provided by the two bitmask fields. The least significant bit is '1' if the section spanning from Y=0 to Y=15 is not completely air, and so forth. For block IDs, metadata, and lighting, the primary bitmask is used. A secondary bitmask is used for 'add' data, which is Mojang's means of provided Block IDs past 256. In vanilla minecraft, you can expect this to always be zero. The sections included in this packet progress from bottom to top, where Y=0 is the bottom.

The data is compressed using the deflate() function in zlib. After uncompressing, the data consists of five (or six) sequential sections, in order:

• Block type array (1 byte per block, 4096 bytes per section)
• Block metadata array (half byte per block, 2048 bytes per section)
• Block light array (half byte per block, 2048 bytes per section)
• Sky light array (half byte per block, 2048 bytes per section)
• Add array (half byte per block, 2048 bytes per section, uses second bitmask)
• Biome array (1 byte per XZ coordinate, 256 bytes total, only sent if 'ground up continuous' is true)

Each section is the concatenated data of all included sections (i.e. the block type array contains the block types of all included sections).

In each section except biome data, your decoder loop should look something like this:

 //Loop over 16x16x16 sections in the 16x256x16 chunk
 for (i=0;i<16;i++) {
   //If the bitmask indicates this chunk has been sent...
   if (bitmask & 1 << i) {
     //Read data...
     cubic_chunk_data = io.read(4096); //2048 for the other arrays, where you'll need to split the data
     
     for(int j=0; j<len(cubic_chunk_data); j++) {
       //Retrieve x,y,z and data from each element in cubic_chunk_array
       
       //Byte arrays
       x = chunk_x*16 + j & 0x0F;
       y = i*16 + j >> 8;
       z = chunk_z*16 + (j & 0xF0) >> 4;
       data = cubic_chunk_data[j]
       
       //Nibble arrays
       data1 = cubic_chunk_data[j] & 0x0F;
       data2 = cubic_chunk_data[j] >> 4;
       
       k = 2*j;
       x1 = chunk_x*16 + k & 0x0F;
       y1 = i*16       + k >> 8;
       z1 = chunk_z*16 + (k & 0xF0) >> 4;
       
       k++;
       x2 = chunk_x*16 + k & 0x0F;
       y2 = i*16       + k >> 8;
       z2 = chunk_z*16 + (k & 0xF0) >> 4;
      }
   }
 }

Each biome byte can have the values from 0 to 22, higher will cause the client to crash.

The 'add' array uses the second bitmask. Block IDs are presumed to be block_id | add << 8

Here's an example of how this packet could be encoded.

Multi Block Change (0x34)

Server to Client

Packet ID	Field Name	Field Type	Example	Notes
0x34	Chunk X	int	-9	Chunk X Coordinate
	Chunk Z	int	12	Chunk Z Coordinate
	Record count	short		The number of blocks affected
	Data size	int		The total size of the data, in bytes. Should always be 4*record count - please confirm.
	Data		…	Coordinates, type, and metadata of blocks to change (see below table).
Total Size:	15 bytes + Arrays

Each record is four bytes.

Bit mask	Width	Meaning
00 00 00 0F	4 bits	Block metadata
00 00 FF F0	12 bits	Block ID
00 FF 00 00	8 bits	Y co-ordinate
0F 00 00 00	4 bits	Z co-ordinate, relative to chunk
F0 00 00 00	4 bits	X co-ordinate, relative to chunk

Block Change (0x35)

Server to Client

Packet ID	Field Name	Field Type	Example	Notes
0x35	X	int	502	Block X Coordinate
	Y	byte	71	Block Y Coordinate
	Z	int	18	Block Z Coordinate
	Block Type	short	78	The new block type for the block
	Block Metadata	byte	0	The new Metadata for the block
Total Size:	13 bytes

Block Action (0x36)

Server to Client

This packet is used for a number of things:

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

Packet ID	Field Name	Field Type	Example	Notes
0x36	X	int	502	Block X Coordinate
	Y	short	71	Block Y Coordinate
	Z	int	18	Block Z Coordinate
	Byte 1	byte	3	Varies depending on block - see below
	Byte 2	byte	17	Varies depending on block - see below
	Block ID	short	29	The block id this action is set for
Total Size:	15 bytes

See Also: Block Actions

Block Break Animation (0x37)

Server to Client

Packet ID	Field Name	Field Type	Example	Notes
0x37	EID?	int		Entity breaking the block?
	X	int		Block position
	Y	int
	Z	int
	Destroy Stage	byte	1	How far destroyed this block is.
Total Size:	18 bytes

Map Chunk Bulk (0x38)

Server to Client

To reduce the number of bytes this packet is used to send chunks together for better compression results. The packet contains up to 100 chunks (later this might be reduced to 50).

The data part is a zlib compressed byte array containing the chunk data. The meta data part specifies which chunks in which order the data part exists of.

To split this packet into chunks you need to uncompress the data array. Then you can iterate through the data part. Each part is 10240 * n + 256 bytes. n is the number of sections in the current chunk (this is the number of flags set in the primary bitmap). 10240 is the amount of bytes for each chunk without add bitmap, 256 bytes are used for biomes. The second short in the meta data part is not yet in use. It could specify if the chunk uses the add bitmap part, because it has very high block ids, but not in the current snapshot.

Packet ID	Field Name	Field Type	Example	Notes
0x38	Chunk Count	short		The number of chunks in this packet
	Chunk data length	int		the size of the data field
	Light Data	boolean		Whether or not the chunk data contains a light nibble array. This is true in the main world, false in the end + nether
	Data	byte array		Compressed chunk data
	meta information	chunk bulk meta information		Chunk count times the Meta information structure (See notes for details)
Total Size:	7 + (Chunk data size) + 12 * (Chunk Count) bytes

Chunk Bulk Meta Information Structure

Field Name	Field Type	Example	Notes
Chunk X	int	10	The X coordinate of the specific chunk
Chunk Z	int	10	The Z coordinate of the specific chunk
Primary bitmap	short	15	A bitmap which specifies which sections are not empty in this chunk
Add bitmap?	short	0	A bitmap which specifies which sections need add information because of very high block ids. not yet used. needs verification
Total Size:	12 bytes

Explosion (0x3C)

Server to Client

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

Packet ID	Field Name	Field Type	Example	Notes
0x3C	X	double
	Y	double
	Z	double
	Radius	float	3.0	Currently unused in the client
	Record count	int		This is the count, not the size. The size is 3 times this value.
	Records	(byte, byte, byte) × count		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
Total Size:	45 bytes + 3*(Record count) bytes

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

Sound Or Particle Effect (0x3D)

Server to Client

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	Field Name	Field Type	Example	Notes
0x3D	Effect ID	int	1003	The ID of the effect, see below.
	X	int		The X location of the effect.
	Y	byte		The Y location of the effect.
	Z	int		The Z location of the effect.
	Data	int	0	Extra data for certain effects, see below.
	Disable relative volume	boolean	false	See above
Total Size:	19 bytes

Effects

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. Data: Record ID
• (1006 not assigned)
• 1007: mob.ghast.charge
• 1008: mob.ghast.fireball
• (1009 not assigned)
• 1010: mob.zombie.wood
• 1011: mob.zombie.metal
• 1012: mob.zombie.woodbreak
• 1013: mob.wither.spawn

Particle:

• 2000: Spawns 10 smoke particles, e.g. from a fire. Data: direction, see below
• 2001: Block break. Data: Block ID
• 2002: Splash potion. Particle effect + glass break sound. Data: Potion ID
• 2003: Eye of ender. Actual client effect to be determined.
• 2004: Mob spawn particle effect: smoke + flames

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

Named Sound Effect (0x3E)

Server to client

Used to play a sound effect on the client.

All known sound effect names can be seen here.

Packet ID	Field Name	Field Type	Example	Notes
0x3E	Sound name	string	step.grass	250
	Effect position X	int	250	effect X multiplied by 8
	Effect position Y	int	250	effect Y multiplied by 8
	Effect position Z	int	250	effect Z multiplied by 8
	Volume	float	9	1 is 100%, can be more
	Pitch	byte	1	63 is 100%, can be more
Total Size:	20 bytes + length of string

Change Game State (0x46)

Server to Client

This packet appeared with protocol version 10. Currently, it appears when a bed can't be used as a spawn point and when the rain state changes. it could have additional uses in the future.

The class has an array of strings linked to reason codes 0, 1, 2, and 3 but only the codes for 1 and 2 are null.

Packet ID	Field Name	Field Type	Example	Notes
0x46	Reason	byte	0
	Game mode	byte	0	Used only when reason = 3. 0 is survival, 1 is creative.
Total Size:	3 bytes

Reason codes

Code	Effect	Text
0	Invalid Bed	"tile.bed.notValid"
1	Begin raining	null
2	End raining	null
3	Change game mode	gameMode.changed
4	Enter credits

Spawn Global Entity (0x47)

Server to Client

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	Field Name	Field Type	Example	Notes
0x47	Entity ID	int	4	The entity ID of the thunderbolt
	Type	byte	1	The global entity type, currently always 1 for thunderbolt.
	X	int	133	Thunderbolt X as Absolute Integer
	Y	int	913	Thunderbolt Y as Absolute Integer
	Z	int	63552	Thunderbolt Z as Absolute Integer
Total Size:	18 bytes

Open Window (0x64)

Server to Client

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	Field Name	Field Type	Example	Notes
0x64	Window id	byte	123	A unique id number for the window to be displayed. Notchian server implementation is a counter, starting at 1.
	Inventory Type	byte	2	The window type to use for display. Check below
	Window title	string	Chest	The title of the window.
	Number of Slots	byte	3	Number of slots in the window (excluding the number of slots in the player inventory).
Total Size:	6 bytes + length of string

The window titles sent by the Notchian server are "Chest", "Large chest", "Crafting", "Furnace", and "Trap". Notchian clients force window titles for some windows, like dispensers and furnaces, but other titles are customizable. However, the window title sent by the server is always used for chests. See inventory windows for further information.

Close Window (0x65)

Two-Way

This packet is sent by the client when closing a 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 message with window id 0 to close their inventory even though there is never an Open Window message for inventory.

Packet ID	Field Name	Field Type	Example	Notes
0x65	Window id	byte	0	This is the id of the window that was closed. 0 for inventory.
Total Size:	2 bytes

Click Window (0x66)

Client to Server

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

Packet ID	Field Name	Field Type	Example	Notes
0x66	Window id	byte	0	The id of the window which was clicked. 0 for player inventory.
	Slot	short	36	The clicked slot. See below.
	Mouse button	byte	1	0: left click, 1: right click, 3: middle click ("shift" is set to 2 in this case)
	Action number	short	12	A unique number for the action, used for transaction handling (See the Transaction packet).
	Shift	boolean	0	This is true if the user was holding keyboard shift when they clicked.
	Clicked item	slot
Total Size:	8 bytes + slot data

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 Action number is actually a counter, starting at 1. This number is used by the server as a transaction ID to send back a Transaction packet.

Set Slot (0x67)

Server to Client

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

Packet ID	Field Name	Field Type	Example	Notes
0x67	Window id	byte	0	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	36	The slot that should be updated
	Slot data	slot
Total Size:	4 bytes + slot data

Note that if window ID and slot are both -1, it means the item currently attached to the cursor.

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

Slots: [1]

Set Window Items (0x68)

Server to Client

The inventory slots

Sent by the server when an item in a slot (in a window) is added/removed. This includes the main inventory, equipped armour and crafting slots.

Packet ID	Field Name	Field Type	Example	Notes
0x68	Window id	byte	1	The id of window which items are being sent for. 0 for player inventory.
	Count	short	4	The number of slots (see below)
	Slot data	array of slots
Total Size:	4 bytes + size of slot data array

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

Update Window Property (0x69)

Server to Client

Packet ID	Field Name	Field Type	Example	Notes
0x69	Window id	byte	2	The id of the window.
	Property	short	1	Which property should be updated.
	Value	short	650	The new value for the property.
Total Size:	6 bytes

Furnace

Properties:

• 0: Progress arrow
• 1: Fire icon (fuel)

Values:

• 0-180 for progress arrow
• 0-250 for fuel indicator

Ranges are presumably in in-game ticks

Enchantment Table

Properties: 0, 1 or 2 depending on the "enchantment slot" being given.

Values: The enchantment's level.

Confirm Transaction (0x6A)

Two-Way

A packet from the server indicating whether a request from the client was accepted, or whether there was a conflict (due to lag). This packet is also sent from the client to the server in response to a server transaction rejection packet.

Packet ID	Field Name	Field Type	Example	Notes
0x6A	Window id	byte	0	The id of the window that the action occurred in.
	Action number	short	12	Every action that is to be accepted has a unique number. This field corresponds to that number.
	Accepted?	boolean	true	Whether the action was accepted.
Total Size:	5 bytes

Creative Inventory Action (0x6B)

Two-Way

While the user is in the standard inventory (i.e., not a crafting bench) on a creative-mode server then the server will send this packet:

• If an item is dropped into the quick bar
• If an item is picked up from the quick bar (item id is -1)

Packet ID	Field Name	Field Type	Example	Notes
0x6B	Slot	short	36	Inventory slot
	Clicked item	slot
Total Size:	3 bytes + slot data

Enchant Item (0x6C)

Client to Server

Packet ID	Field Name	Field Type	Example	Notes
0x6C	Window ID	byte	1	The ID sent by Open Window
	Enchantment	byte	0	The position of the enchantment on the enchantment table window, starting with 0 as the topmost one.
Total Size:	3 bytes

Update Sign (0x82)

Two-Way

Packet ID	Field Name	Field Type	Example	Notes
0x82	X	int	128	Block X Coordinate
	Y	short	0	Block Y Coordinate
	Z	int	-128	Block Z Coordinate
	Text1	string	First line	First line of text in the sign
	Text2	string	Second line	Second line of text in the sign
	Text3	string	Third line	Third line of text in the sign
	Text4	string	Fourth line	Fourth line of text in the sign
Total Size:	11 bytes + 4 strings

This message is sent from the server to the client whenever a sign is discovered or created. This message is sent from the client to the server when the "Done" button is pushed after placing a sign. This message is NOT sent when a sign is destroyed or unloaded.

Item Data (0x83)

Server to Client

Sent to specify complex data on an item; currently used only for maps.

Packet ID	Field Name	Field Type	Example	Notes
0x83	Item Type	short	358	Type of item being modified
	Item ID	short	0	The ID (damage value) of the item being modified
	Text length	short	35	Length of following byte array
	Text	byte array	{0,0,0,20,20,20,20,20}	ASCII text.
Total Size:	7 bytes + Text length

Maps If the first byte of the text is 0, the next two bytes are X start and Y start and the rest of the bytes are the colors in that column.

If the first byte of the text is 1, the rest of the bytes are in groups of three: (data, x, y). The lower half of the data is the type (always 0 under vanilla) and the upper half is the direction.

Update Tile Entity (0x84)

Server to Client

Essentially a block update on a tile entity.

Packet ID	Field Name	Field Type	Example	Notes
0x84	X	int
	Y	short
	Z	int
	Action	byte		The type of update to perform
	Data length	Short		Varies
	NBT Data	Byte Array - Present if data length > 0		Compressed with gzip. Varies
Total Size:	12 + itemstack bytes

Actions

• 1: Set mob displayed inside a mob spawner. Custom 1 contains the mob type

Increment Statistic (0xC8)

Server to Client

Packet ID	Field Name	Field Type	Example	Notes
0xC8	Statistic ID	int	1003	The ID of the statistic. See List of statistics.
	Amount	byte	1	The amount to increment the statistic.
	Total Size:	6 bytes

Player List Item (0xC9)

Server to Client

Sent by the notchian server to update the user list (<tab> in the client). The server sends one packet per user per tick, amounting to 20 packets/s for 1 online user, 40 for 2, and so forth.

Packet ID	Field Name	Field Type	Example	Notes
0xC9	Player name	string	barneygale	Supports chat colouring, limited to 16 characters.
	Online	boolean	true	If false, the client will remove the user from the list.
	Ping	short	193	Ping, presumably in ms.
Total Size:	6 bytes + length of string

Player Abilities (0xCA)

Two-Way

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

These booleans are whether damage is disabled (god mode), whether the player is flying, whether the player can fly, and whether the player is in creative mode.

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. 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	Field Name	Field Type	Example	Notes
0xCA	Flags	byte	5
	Flying speed	byte	12
	Walking speed	byte	25
	Total Size:	4 bytes

Tab-complete (0xCB)

Two-way

Sent C->S when the user presses [tab] while writing text. The payload contains all text behind the cursor.

The server responds with an auto-completion 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.

In the event of more than one possible completion, the server responds with the options packed into the single string field, separated by a null character. Note that as strings are UTF-16, this is two bytes wide.

Packet ID	Field Name	Field Type	Example	Notes
0xCB	Text	string
Total Size:	3 bytes + length of string

Client Settings (0xCC)

Client to server

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

Packet ID	Field Name	Field Type	Example	Notes
0xCC	Locale	string	en_GB
	View distance	byte	0	0-3 for 'far', 'normal', 'short', 'tiny'.
	Chat flags	byte	8	Chat settings. See notes below.
	Difficulty	byte	0	Client-side difficulty from options.txt
	Show Cape	boolean	true	Client-side "show cape" option
Total Size:	7 bytes + length of string

Chat flags has several values packed into one byte.

Chat Enabled: Bits 0-1. 00: Enabled. 01: Commands only. 10: Hidden.

Colors Enabled: Bit 3. 0: Disabled. 1: Enabled.

Client Statuses (0xCD)

Client to server

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

Packet ID	Field Name	Field Type	Example	Notes
0xCD	Payload	byte	0	Bit field. 0: Initial spawn, 1: Respawn after death
Total Size:	2 bytes

Plugin Message (0xFA)

Two-Way

Mods and plugins can use this to send their data. As of 1.3, Minecraft itself uses a number of plugin channels. These internal channels are prefixed with MC|.

Packet ID	Field Name	Field Type	Example	Notes
0xFA	Channel	string	MyMod:testchannel	Name of the "channel" used to send the data.
	length	short		Length of the following byte array
	data	byte array		Any data.
Total Size:	5 bytes + length of string + length of byte array

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

Encryption Key Response (0xFC)

Two-Way

See Protocol Encryption for information on this packet. Bypassing the encryption is possible, authentication for the player name is still needed if the server is in online mode, but instead of sending this packet, you send Client Statuses instead.

Packet ID	Field Name	Field Type	Example	Notes
0xFC	Shared secret length	short
	Shared secret	byte array
	Verify token length	short
	Verify token response	byte array
Total Size:	5 bytes + length of shared secret + length of token

Encryption Key Request (0xFD)

Server to client

See Protocol Encryption for information on this packet.

Packet ID	Field Name	Field Type	Example	Notes
0xFD	Server id	string
	Public key length	short
	Public key	byte array
	Verify token length	short
	Verify token	byte array
Total Size:	7 bytes + length of string + length of key + length of token

Server List Ping (0xFE)

Client to Server

This packet is used by the multiplayer menu to retrieve MOTD, version, and player counts. For more info see Server List Ping

Packet ID	Field Name	Field Type	Example	Notes
0xFE	Magic	byte	1	always 1
Total Size:	2 bytes

Disconnect/Kick (0xFF)

Two-Way

Sent by the server before it disconnects a client, or by the client before it disconnects from the server. The receiver of this packet assumes that the sender has already closed the connection by the time the packet arrives.

Due to race conditions in the client, a local server may need to pause for a short period after sending this packet before closing the connection. An alternative is simply not to close the connection, and wait for the client to do so on receipt of this packet.

Packet ID	Field Name	Field Type	Example	Notes
0xFF	Reason	string	The server is full!	Displayed to the client when the connection terminates
Total Size:	3 bytes + length of strings

See Also

• Protocol History
• Data Types
• Units of Measurement