Pre-release protocol

This page documents the changes from the last stable Minecraft release (currently 1.7.4, protocol 4) to the current pre-release. Note that this page contains bleeding-edge information that may not be completely or correctly documented. He who wishes to commandeer the merging of this into Protocol when an update is made must be sure to respect any changes that may have occured to the respective packets there.

Protocol History

14w31a

• The length prefix on the payload of Plugin Message has been removed (Both ways)
• Added new Resource Pack Send packet (Clientbound)
• Added new Resource Pack Status packet (Serverbound)
• Added VarLong data type
• Changed a few fields in World Border to VarLong

14w29a

• Fix the length prefix of Plugin Message so that its a Varint instead of an unsigned short
• Added "Reduced Debug Info" boolean to Join Game
• Added "Long Distance" boolean to Particle

14w28b

• Uncompressed NBT
• Added Display name fields to Player List Item
• New 'Player List Header/Footer' packet

14w28a

• Changed Chunk packets to remove compression
• Added packets to toggle compression/set threshold
• Allowed compression for the whole protocol
• Changed the Maps packet

14w26c

• Changed Multi Block Change to using packed block ids
• Changed Block Change to using packed block ids

14w26b

• Bug fix

14w26a

• Changed chunk sending

14w25b

• Added boolean field to all entity movement packets

14w25a

• Update Sign now uses Chat

14w21a

• All byte arrays have VarInt length prefixes instead of short
• Spawn Player changes
• Player list item changes

14w20a

• Added new packet 'Title'

14w19a

• Changed the Particle's 'Particle Name' to an int
• Added a new field to Particle
• Rewrote Player List Item
• Added SET_WARNING_TIME and SET_WARNING_BLOCKS to World Border
• Added new serverbound packet Spectate

14w18b

• Bugfix

14w18a

• Added 'INITIALIZE' action to World Border

14w17a

• Increased the max payload size of 'Plugin Message' from 32767 to 1048576 (Broken because of incorrect data type)
• Added new packet 'World Border'

14w11a

• UUIDs now include the '-'s

14w08a

• Added new field 'Type' to Scoreboard Objective

14w07a

• Added two new fields to Teams

14w06a

Clientbound

• Added new field 'Hide Particles' to Entity Effect

Serverbound

• Removed 'HeadY' from Player Position
• Removed 'HeadY' from Player Position And Look

14w05a

Clientbound

• New packet 'Camera'

14w04b

• Spawn Painting now uses the 'Position' data type
• Changed Spawn Painting's Direction type to Unsigned Byte

14w04a

• Encoding for 'Position' changed

Clientbound

• Changed Entity Equipment's EntityId type to VarInt
• Changed Update Health's Food type to VarInt
• Changed Use Bed's EntityId type to VarInt
• Added new fields to Spawn Player
• Changed Collect Item's EntityId(s) types to VarInt
• Changed Entity Velocity's EntityId type to VarInt
• Changed Destroy Entities' Length type to VarInt
• Changed Destroy Entities' EntityIds type to VarInt array
• Changed Entity's EntityId type to VarInt
• Changed Entity Relative Move's EntityId type to VarInt
• Changed Entity Look's EntityId type to VarInt
• Changed Entity Look and Relative Move's EntityId type to VarInt
• Changed Entity Teleport's EntityId type to VarInt
• Changed Entity Head Look's EntityId type to VarInt
• Changed Entity Metadata's EntityId type to Varint
• Changed Entity Effect's EntityId type to VarInt
• Changed Entity Effect's Duration type to VarInt
• Changed Remove Entity Effect's EntityId type to VarInt
• Changed Set Experience's Level type to VarInt
• Changed Set Experience's Total Experience type to VarInt
• Changed Entity Properties's EntityId type to VarInt
• Changed Entity Properties's List Length type to VarInt
• Changed Player List Item's Ping type to VarInt
• Changed Update Score's Value type to VarInt
• Changed Teams' Player count type to VarInt
• New packet 'Combat Event'

Serverbound

• Changed Keep Alive's Keep Alive ID type to VarInt
• Changed Use Entity's Target type to VarInt
• Changed Use Entity's Mouse type to Unsigned Byte
• Removed everything from Animation
• Changed Entity Action's EntityId type to VarInt
• Changed Entity Action's Action ID type to Unsigned Byte
• Changed Entity Action's Values
• Changed Entity Action's Jump Boast type to VarInt
• Merged Steer Vehicle's Jump and Unmount into a Bit Field
• Changed Client Status's Action ID type to Unsigned Byte

14w03a

• New data type 'Position'

Clientbound

• Spawn Position now uses the 'Position' data type
• Use Bed now uses the 'Position' data type
• Block Change now uses the 'Position' data type
• Block Action now uses the 'Position' data type
• Block Break Animation now uses the 'Position' data type
• Effect now uses the 'Position' data type
• Sign Update now uses the 'Position' data type
• Update Block Entity now uses the 'Position' data type
• Sign Editor Open nows uses the 'Position' data type

Serverbound

• Player Digging now uses the 'Position' data type
• Player Block Placement now uses the 'Position' data type
• Update Sign now uses the 'Position' data type
• Client Settings 'show cape' type changed from boolean to unsigned byte

14w02a

• Added 'Position' to Chat Message Clientbound
• Remove Player Position And Look's 'OnGround' clientbound
• Added 'Flags' to Player Position And Look clientbound
• Changed Open Inventory's 'Inventory Type' type from byte to string
• Added Server Difficulty
• Removed Client Settings' 'Difficulty'

Protocol Version

Version	Protocol
14w02a	5
14w03a	6
14w04a	7
14w04b	8
14w05a	9
14w06a	10
14w07a	11
14w08a	12
14w11a	14
14w17a	15
14w18b	16
14w19a	17
14w20a	18
14w21a	19
14w21b	20
14w25a	21
14w25b	22
14w26a	23
14w26b	24
14w26c	25
14w27a/b	26
14w28a	27
14w28b	28
14w29a	29
14w30a	30
14w30c	31
14w31a	32

Packet format

Once a Set Compression packet is sent, compression is enabled for all following packets. The format of a packet changes slighty to include the size of the uncompressed packet.

Name	Type
Packet Length	VarInt
Data Length	VarInt
Data

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

If compressed, the data's length 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 threshold of -1.

New data types

Position

Encoded as followed:

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

And decoded as:

 long val; // Encoded value
 x = val >> 38;
 y = val << 26 >> 52
 z = val << 38 >> 38

VarLong

Like VarInt but based on java's long type instead of int

Play

Clientbound

Join Game

See Protocol Encryption for information on logging in.

Packet ID	Category	Bound To	Field Name	Field Type	Notes
0x01	Play	Client	Entity ID	Int	The player's Entity ID
			Gamemode	Unsigned Byte	0: survival, 1: creative, 2: adventure. Bit 3 (0x8) is the hardcore flag
			Dimension	Byte	-1: nether, 0: overworld, 1: end
			Difficulty	Unsigned Byte	0 thru 3 for Peaceful, Easy, Normal, 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 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	Field Name	Field Type	Notes
0x02	JSON Data	String	Chat , Limited to 32767 bytes
	Position	Byte	0 - Chat (chat box) ,1 - System Message (chat box), 2 - Above action bar

Malformed JSON will disconnect the client

Entity Equipment

Packet ID	Field Name	Field Type	Notes
0x04	EntityID	VarInt	Entity's ID
	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	Field Name	Field Type	Notes
0x05	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	Field Name	Field Type	Notes
0x06	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

Player Position And Look

Updates the players 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 will result in the client being 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 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)

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.

Packet ID	Field Name	Field Type	Notes
0x08	X	Double	Absolute/Relative position
	Y	Double	Absolute/Relative position
	Z	Double	Absolute/Relative position
	Yaw	Float	Absolute/Relative rotation on the X Axis, in degrees
	Pitch	Float	Absolute/Relative rotation on the Y Axis, in degrees
	Flags	Byte	X 0x01 Y 0x02 Z 0x04 Y_ROT 0x08 X_ROT 0x10

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	Field Name	Field Type	Notes
0x0A	Entity ID	VarInt	Player ID
	Location	Position	Block location of the head part of the bed

Spawn Player

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.

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 :)

Packet ID	Field Name		Field Type	Notes
0x0C	Entity ID		VarInt	Player's Entity ID
	Player UUID		UUID	Player's UUID
	X		Int	Player X as a Fixed-Point number
	Y		Int	Player X as a Fixed-Point number
	Z		Int	Player X as a Fixed-Point number
	Yaw		Byte	Player rotation as a packed byte
	Pitch		Byte	Player rotation as a packet byte
	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. A negative value crashes clients.
	Metadata		Metadata	The client will crash if no metadata is sent

The client will crash if no metadata is sent The client will disconnect if both UUID and Name are empty

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 & Look packet sent by the client.

Packet ID	Field Name	Field Type	Notes
0x0D	Collected Entity ID	VarInt
	Collector Entity ID	VarInt

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	Field Name	Field Type	Notes
0x10	Entity ID	VarInt	Entity's ID
	Title	String	Name of the painting. Max length 13
	Location	Position	Center coordinates
	Direction	Unsigned Byte	Direction the painting faces (0 -z, 1 -x, 2 +z, 3 +x)

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	Field Name	Field Type	Notes
0x12	Entity ID	VarInt	Entity's ID
	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 an list of Entities is to be destroyed on the client.

Packet ID	Field Name	Field Type	Notes
0x13	Count	VarInt	Length of following array
	Entity IDs	Array of VarInt	The list of entities of destroy

Entity

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	Notes
0x14	Entity ID	VarInt	Entity's ID

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	Field Name	Field Type	Notes
0x15	Entity ID	VarInt	Entity's ID
	DX	Byte	Change in X position as a Fixed-Point number
	DY	Byte	Change in Y position as a Fixed-Point number
	DZ	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. Example: "Yaw" field 64 means a 90 degree turn.

Packet ID	Field Name	Field Type	Notes
0x16	Entity ID	VarInt	Entity's ID
	Yaw	Byte	The X Axis rotation as a fraction of 360
	Pitch	Byte	The Y Axis rotation as a fraction of 360
	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	Field Name	Field Type	Notes
0x17	Entity ID	VarInt	Entity's ID
	DX	Byte	Change in X position as a Fixed-Point number
	DY	Byte	Change in Y position as a Fixed-Point number
	DZ	Byte	Change in Z position as a Fixed-Point number
	Yaw	Byte	The X Axis rotation as a fraction of 360
	Pitch	Byte	The Y Axis rotation as a fraction of 360
	On Ground	Boolean

Entity Teleport

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

Packet ID	Field Name	Field Type	Notes
0x18	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
	Yaw	Byte	The X Axis rotation as a fraction of 360
	Pitch	Byte	The Y Axis rotation as a fraction of 360
	On Ground	Boolean

Entity Head Look

Changes the direction an entity's head is facing.

Packet ID	Field Name	Field Type	Notes
0x19	Entity ID	VarInt	Entity's ID
	Head Yaw	Byte	Head yaw in steps of 2p/256

Entity Metadata

Packet ID	Field Name	Field Type	Notes
0x1C	Entity ID	VarInt	Entity's ID
	Metadata	Metadata

Entity Effect

Packet ID	Field Name	Field Type	Notes
0x1D	Entity ID	VarInt	Entity's ID
	Effect ID	Byte	See [[1]]
	Amplifier	Byte
	Duration	VarInt
	Hide Particles	Boolean

Remove Entity Effect

Packet ID	Field Name	Field Type	Notes
0x1E	Entity ID	VarInt	Entity's ID
	Effect ID	Byte

Set Experience

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

Packet ID	Field Name	Field Type	Notes
0x1F	Experience bar	Float	Between 0 and 1
	Level	VarInt
	Total Experience	VarInt

Entity Properties

Packet ID	Field Name	Field Type	Notes
0x20	Entity ID	VarInt	Entity's ID
	Count	Int	Length of following array
	Properties	Array of Property Data

Property Data structure:

Field Name	Field Type	Notes
Key	String
Value	Double
List Length	VarInt	Number of list elements that follow.
Modifiers	Array of Modifier Data	http://www.minecraftwiki.net/wiki/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	128-bit integer
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 14w26a:

• Data value section removed
• Extended id section removed
• Block id section is now a unsigned short per a block
• The block id is equal to (id << 4) | data

Packet ID	Category	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 map specifies exactly which sections are included, and which are air
			Primary bit map	Unsigned Short	Bitmask with 1 for every 16x16x16 section which data follows in the compressed data.
			Size	VarInt	Size of chunk data
			Data	Byte array	The chunk data is not compressed as of 14w28a

Multi Block Change

Packet ID	Category	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	The number of blocks affected
			Records	Array of Records

Record

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

Packet ID	Field Name	Field Type	Notes
0x23	Location	Position	Block Coordinates
	Block ID	VarInt	data

Block Action

This packet is used for a number of things:

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

See Also: Block Actions

Packet ID	Field Name	Field Type	Notes
0x24	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 loose it's transparency)

Packet ID	Field Name	Field Type	Notes
0x25	Entity ID	VarInt	Entity's ID
	Location	Position	Block Position
	Destroy Stage	Byte	0 - 9

Map Chunk Bulk

See also: SMP Map Format

Snapshot changes at #Chunk_Data

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

Packet ID	Category	Bound To	Field Name	Field Type	Notes
0x26	Play	Client	Sky light sent	Bool	Whether or not the chunk data contains a light nibble array. This is true in the main world, false in the end + nether
			Chunk column count	VarInt	The number of chunk in this packet
			Meta information	Meta	See below
			Data	Byte Array	Chunk data. Uncompressed as of 14w28a

Meta

Field Name	Field Type	Notes
Chunk X	Int	The X Coordinate of the chunk
Chunk Z	Int	The Z Coordinate of the chunk
Primary bitmap	Unsigned Short	A bitmap which specifies which sections are not empty in this chunk

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	Field Name	Field Type	Notes
0x28	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	Bool	See above

Effects

ID	Name
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	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. 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 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

Particle

Displays the named particle

Packet ID	Field Name	Field Type	Notes
0x2A	Particle Id	Int
	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
	Number of particles	Int	The number of particles to create
	Data	Array of VarInt	Length depends on particle. ICON_CRACK, BLOCK_CRACK, and BLOCK_DUST have lengths of 2, the rest have 0.

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	Field Name	Field Type	Notes
0x2D	Window id	Unsigned Byte	A unique id number for the window to be displayed. Notchian server implementation is a counter, starting at 1.
	Inventory Type	String	The window type to use for display. Check below
	Window title	String (JSON)	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	Int	EntityHorse's entityId. Only sent when window type is equal to "EntityHorse".

See inventory windows for further information.

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	Field Name	Field Type	Notes
0x33	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

Maps

Packet ID	Category	Bound To	Field Name	Field Type	Notes
0x34	Play	Client	Item Damage	VarInt	The damage value of the map being modified
			Scale	Byte
			Length	VarInt
			Icons	3 * length bytes	First byte, 0xF0 = Direction, 0x0F = Type. Second byte, X. Third byte, Y
			Columns	Byte
			Rows	Byte	Only if Columns is more than 0
			X	Byte	Only if Columns is more than 0
			Y	Byte	Only if Columns is more than 0
			Length	VarInt	Only if Columns is more than 0
			Data	Length bytes	Only if Columns is more than 0

Update Block Entity

Essentially a block update on a block entity.

Packet ID	Field Name	Field Type	Notes
0x35	Location	Position
	Action	Unsigned Byte	The type of update to perform
	Data length	Short	Varies
	NBT Data	Byte Array	Present if data length > 0. Varies

Actions

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

Sign Editor Open

Sent on placement of sign.

Packet ID	Field Name	Field Type	Notes
0x36	Location	Position	Block coordinates

Player List Item

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

Packet ID	Field Name		Field Type	Notes
0x38	Action		VarInt
	Length		VarInt	The follow fields are repeated length times
	UUID		UUID	The uuid of the player
	0 (ADD_PLAYER)	Name	String
		Array of properties	Properties	VarInt length. Each properties is as followed: Name(String), Value(String), IsSigned(Boolean) and Signature(String, only if isSigned is true)
		Gamemode	VarInt
		Ping	VarInt
		Has Display Name	Boolean
		Display Name	Chat	Only send if Has Diplay Name is true
	1 (UPDATE_GAMEMODE)	Gamemode	VarInt
	2 (UPDATE_LATENCY)	Ping	VarInt
	3 (UPDATE_DISPLAY_NAME)	Has Display Name	Boolean
		Display Name	Chat	Only send if Has Diplay Name is true
	4 (REMOVE_PLAYER)

Scoreboard Objective

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

Packet ID	Field Name	Field Type	Notes
0x3B	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	String	Only if mode is 0 or 2. The text to be displayed for the score.
	Type	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	Field Name	Field Type	Notes
0x3C	Item Name	String	An unique name to be displayed in the list.
	Update/Remove	Byte	0 to create/update an item. 1 to remove an item.
	Score Name	String	The unique name for the scoreboard to be updated. Only sent when Update/Remove does not equal 1.
	Value	VarInt	The score to be displayed next to the entry. Only sent when Update/Remove does not equal 1.

The final String and Int are only sent if the Update/Remove Byte does not equal 1

Teams

Creates and updates teams.

Packet ID	Field Name	Field Type	Notes
0x3E	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	String	Only if Mode = 0 or 2.
	Team Prefix	String	Only if Mode = 0 or 2. Displayed before the players' name that are part of this team.
	Team Suffix	String	Only if Mode = 0 or 2. Displayed after the players' name that are part of this team.
	Friendly fire	Byte	Only if Mode = 0 or 2; 0 for off, 1 for on, 3 for seeing friendly invisibles
	Name Tag Visibility	String	Only if Mode = 0 or 2. always, hideForOtherTeams, hideForOwnTeam, never.
	Color	Byte	Only if Mode = 0 or 2. Same as Chat colors.
	Player count	VarInt	Only if Mode = 0 or 3 or 4. Number of players in the array
	Players	Array of strings	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	Category	Bound To	Field Name	Field Type	Notes
0x3F	Play	Client	Channel	String	Name of the "channel" used to send the data.
			Data	Byte Array	Any data.

Server Difficulty

Changes the difficulty setting in the client's option menu

Packet ID	Field Name	Field Type	Notes
0x41	Difficulty	Unsigned Byte	0:PEACEFUL, 1:EASY, 2:NORMAL, 3: HARD

Combat Event

Packet ID	Field Name	Field Type	Notes
0x42	Event	Unsigned Byte	0 ENTER_COMBAT, 1 END_COMBAT, 2 ENTITY_DEAD
	Duration	VarInt	Only for END_COMBAT
	Entity ID	Int	Only for END_COMBAT
	Player ID	VarInt	Only for ENTITY_DEAD
	Entity ID	Int	Only for ENTITY_DEAD
	Message	String	Only for ENTITY_DEAD

Camera

Packet ID	Field Name	Field Type	Notes
0x43	Camera ID	VarInt

World Border

Packet ID	Field Name		Field Type	Notes
0x44	Action		VarInt
	Action	Name
	0 (SET_SIZE)	Radius	Double
	1 (LERP_SIZE)	Old radius	Double
		New radius	Double
		Speed	VarLong
	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
	5 (SET_WARNING_BLOCKS)	Warning blocks	VarInt

Title

Packet ID	Field Name		Field Type	Notes
0x45	Action		VarInt
	Action	Name
	0 (TITLE)	Text	JSON Chat String
	1 (SUBTITLE)	Text	JSON Chat String
	2 (TIMES)	Fade In	Int
		Stay	Int
		Fade Out	Int
	3 (CLEAR)
	4 (RESET)

Set Compression

Packet ID	Field Name	Field Type	Notes
0x46	Threshold	VarInt	Threshold is the max size of a packet before its compressed

Player List Header/Footer

Packet ID	Field Name	Field Type	Notes
0x47	Header	Chat
	Footer	Chat

Resource Pack Send

Packet ID	Field Name	Field Type	Notes
0x48	URL	String
	Hash	String	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

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	Field Name	Field Type	Notes
0x00	Keep Alive ID	VarInt

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	Field Name	Field Type	Notes
0x02	Target	VarInt
	Mouse	Unsigned Byte	0 = Left-click, 1 = Right-click

Player Position

Updates the players XYZ position on the server. If HeadY - FeetY 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 fixed-point 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	Notes
0x04	X	Double	Absolute position
	FeetY	Double	Absolute feet position, normally HeadY - 1.62. Used to modify the players bounding box when going up stairs, crouching, etc…
	Z	Double	Absolute position
	On Ground	Bool	True if the client is on the ground, False otherwise

Player Position And Look

A combination of Player Look and Player position.

Packet ID	Field Name	Field Type	Notes
0x06	X	Double	Absolute position
	FeetY	Double	Absolute feet position. Is normally HeadY - 1.62. Used to modify the players bounding box when going up stairs, crouching, etc…
	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	Bool	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	Field Name	Field Type	Notes
0x07	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

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

Packet ID	Field Name	Field Type	Notes
0x08	Location	Position	Block position
	Direction	Byte	The offset to use for block/item placement (see below)
	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 (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.

Animation

Packet ID	Field Name	Field Type	Notes
0x0A

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	Field Name	Field Type	Notes
0x0B	Entity ID	VarInt	Player ID
	Action ID	Unsigned Byte	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	Field Name	Field Type	Notes
0x0C	Sideways	Float	Positive to the left of the player
	Forward	Float	Positive forward
	Flags	Unsigned Byte	0x1 Jump, 0x2 Unmount

Update Sign

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

Packet ID	Field Name	Field Type	Notes
0x12	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

Client Settings

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

Packet ID	Field Name	Field Type	Notes
0x15	Locale	String	en_GB
	View distance	Byte	Client-side render distance(chunks)
	Chat flags	Byte	Chat settings. See notes below.
	Chat colours	Bool	"Colours" multiplayer setting
	Displayed skin parts	Unsigned Byte	Unknown

Chat flags has several values packed into one byte.

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

Client Status

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	Notes
0x16	Action ID	Unsigned Byte	See below

Action ID values:

Action ID	Name
0	Perform respawn
1	Request stats
2	Open 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/

Packet ID	Category	Bound To	Field Name	Field Type	Notes
0x17	Play	Server	Channel	String	Name of the "channel" used to send the data.
			Data	Byte Array	Any data.

Spectate

Packet ID	Field Name	Field Type	Notes
0x18	Target Player	UUID

Resource Pack Status

Packet ID	Field Name	Field Type	Notes
0x19	Hash	String
	Result	VarInt	Successfully loaded: 0, Declined: 1, Failed download: 2, Accepted: 3

Data

Slot Data

See also Slot Data

Field Name	Field Type	Notes
Block ID	short	-1 for empty slots
Item count	byte
Item damage	short
Data	NBT	Uncompressed NBT data without length prefix. This had previously a short length prefix and was compressed.

Login

The login process is as follows:

   C->S : Handshake State=2
   C->S : Login Start
   S->C : Encryption Key Request
   (Client Auth)
   C->S : Encryption Key Response
   (Server Auth, Both enable encryption)
   S->C : Login Success

For unauthenticated and localhost connections there is no encryption. In that case Login Start is directly followed by Login Success.

See Protocol Encryption for details.

Clientbound

Encryption Request

Packet ID	Category	Bound To	Field Name	Field Type	Notes
0x01	Login	Client	Server ID	String	appears to be empty as of 1.7.x
			Length	VarInt	length of public key
			Public Key	Byte array
			Length	VarInt	length of verify token
			Verify Token	Byte array

See Protocol Encryption for details.

Set Compression

Packet ID	Field Name	Field Type	Notes
0x03	Threshold	VarInt	Threshold is the max size of a packet before its compressed

Serverbound

Encryption Response

Packet ID	Category	Bound To	Field Name	Field Type	Notes
0x01	Login	Server	Length	VarInt	length of shared secret
			Shared Secret	Byte array
			Length	VarInt	length of verify token
			Verify Token	Byte array

See Protocol Encryption for details.