Protocol

This page presents a dissection of the current stable Minecraft protocol. The current pre-release protocol is documented elsewhere. The protocol for Pocket Minecraft is substantially different, and is documented at Pocket 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.

As of 1.7 strings are now UTF-8 (prefixed with a VarInt giving the string's length in bytes) instead of UTF-16.

As of 1.7.6 all UUIDs used in the protocol now contain '-'. The session server still returns them without

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 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.
See also: Data types, Units of Measurement

The changes between versions may be viewed at Protocol History

Packets

Protocol Version

1.7.2 - 4

1.7.6 - 5

Packet format

Field Name	Field Type	Notes
Length	VarInt	Length of packet data + length of the packet ID
Packet ID	VarInt
Data

Handshaking

Serverbound

Handshake

This causes the server to switch into the target state.

Packet ID	Field Name	Field Type	Notes
0x00	Protocol Version	VarInt	(4 as of 1.7.2)
	Server Address (hostname or IP)	String	localhost
	Server Port	Unsigned Short	25565
	Next state	VarInt	1 for status, 2 for login

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.

Packet ID	Field Name	Field Type	Notes
0x00	Keep Alive ID	Int

Join Game

Packet ID	Field Name	Field Type	Notes
0x01	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

If the Dimension isn't valid then the client will crash

Chat Message

Packet ID	Field Name	Field Type	Notes
0x02	JSON Data	String	https://gist.github.com/thinkofdeath/e882ce057ed83bac0a1c , Limited to 32767 bytes

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	Field Name	Field Type	Notes
0x03	Age of the world	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	Field Name	Field Type	Notes
0x04	EntityID	Int	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	X	Int	Spawn X in block coordinates
	Y	Int	Spawn Y in block coordinates
	Z	Int	Spawn Z in block coordinates

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

If the Dimension isn't valid then the client will crash

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 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)

Packet ID	Field Name	Field Type	Notes
0x08	X	Double	Absolute position
	Y	Double	Absolute position (eyes pos)
	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

Held Item Change

Sent to change the player's slot selection

Packet ID	Field Name	Field Type	Notes
0x09	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	Field Name	Field Type	Notes
0x0A	Entity ID	Int	Player ID
	X	Int	Bed headboard X as block coordinate
	Y	Unsigned Byte	Bed headboard Y as block coordinate
	Z	Int	Bed headboard Z as block coordinate

Animation

Sent whenever an entity should change animation.

Packet ID	Field Name	Field Type	Notes
0x0B	Entity ID	VarInt	Player ID
	Animation	Unsigned Byte	Animation ID

Animation can be one of the following values:

ID	Animation
0	Swing arm
1	Damage animation
2	Leave bed
3	Eat food
4	Critical effect
5	Magic critical effect
102	(unknown)
104	Crouch
105	Uncrouch

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		String	Player's UUID
	Player Name		String	Player's Name
	Data count		VarInt
	Data	Name	String	Name of the property as return by the session server's /hasJoined. E.g: textures
		Value	String	Value of the property (base64) as return by the session server's /hasJoined
		Signature	String	Signature of the property (base64) as return by the session server's /hasJoined.
	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	Int
	Collector Entity ID	Int

Spawn Object

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

Packet ID	Field Name	Field Type	Notes
0x0E	Entity ID	VarInt	Entity ID 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	Byte	The pitch in steps of 2p/256
	Yaw	Byte	The yaw in steps of 2p/256
	Data	Object Data

Spawn Mob

Sent by the server when a Mob Entity is Spawned

Packet ID	Field Name	Field Type	Notes
0x0F	Entity ID	VarInt	Entity's ID
	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
	Pitch	Byte	The pitch in steps of 2p/256
	Head Pitch	Byte	The pitch in steps of 2p/256
	Yaw	Byte	The yaw in steps of 2p/256
	Velocity X	Short
	Velocity Y	Short
	Velocity Z	Short
	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	Field Name	Field Type	Notes
0x10	Entity ID	VarInt	Entity's ID
	Title	String	Name of the painting. Max length 13
	X	Int	Center X coordinate
	Y	Int	Center Y coordinate
	Z	Int	Center Z coordinate
	Direction	Int	Direction the painting faces (0 -z, 1 -x, 2 +z, 3 +x)

Spawn Experience Orb

Spawns one or more experience orbs.

Packet ID	Field Name	Field Type	Notes
0x11	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	Field Name	Field Type	Notes
0x12	Entity ID	Int	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	Byte	Length of following array
	Entity IDs	Array of Int	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	Int	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	Int	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

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	Int	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

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	Int	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

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	Int	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

Entity Head Look

Changes the direction an entity's head is facing.

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

Entity Status

Packet ID	Field Name	Field Type	Notes
0x1A	Entity ID	Int	Entity's ID
	Entity Status	Byte	See below

Entity Status	Meaning
0	Something related to living entities?
1	Something related to the player entity?
2	Entity hurt
3	Entity dead
4	Iron Golem throwing up arms
6	Wolf taming
7	Wolf tamed
8	Wolf shaking water off itself
9	(of self) Eating accepted by server
10	Sheep eating grass
11	Iron Golem handing over a rose
12	Spawn "heart" particles near a villager
13	Spawn particles indicating that a villager is angry and seeking revenge
14	Spawn happy particles near a villager
15	Spawn a "magic" particle near the Witch
16	Zombie converting into a villager by shaking violently (unused in recent update)
17	A firework exploding
18	Fall in love with human?

Attach Entity

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

Packet ID	Field Name	Field Type	Notes
0x1B	Entity ID	Int	Entity's ID
	Vehicle ID	Int	Vechicle's Entity ID
	Leash	Bool	If true leashes the entity to the vehicle

Entity Metadata

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

Entity Effect

Packet ID	Field Name	Field Type	Notes
0x1D	Entity ID	Int	Entity's ID
	Effect ID	Byte	See [[1]]
	Amplifier	Byte
	Duration	Short

Remove Entity Effect

Packet ID	Field Name	Field Type	Notes
0x1E	Entity ID	Int	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	Short
	Total Experience	Short

Entity Properties

Packet ID	Field Name	Field Type	Notes
0x20	Entity ID	Int	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	Short	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

Packet ID	Field Name	Field Type	Notes
0x21	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.
	Add bit map	Unsigned Short	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	Byte array	The chunk data is compressed using Zlib Deflate

Multi Block Change

Packet ID	Field Name	Field Type	Notes
0x22	Chunk X	Int	Chunk X coordinate
	Chunk Z	Int	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
	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	X	Int	Block X Coordinate
	Y	Unsigned Byte	Block Y Coordinate
	Z	Int	Block Z Coordinate
	Block ID	VarInt	The new block ID for the block
	Block Metadata	Unsigned Byte	The new metadata for the block

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	X	Int	Block X Coordinate
	Y	Short	Block Y Coordinate
	Z	Int	Block Z Coordinate
	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
	X	Int	Block Position
	Y	Int
	Z	Int
	Destroy Stage	Byte	0 - 9

Map Chunk Bulk

See also: SMP Map Format

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

Packet ID	Field Name	Field Type	Notes
0x26	Chunk column count	Short	The number of chunk in this packet
	Data length	Int	The size of the data field
	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
	Data	Byte Array	Compressed chunk data
	Meta information	Meta	See below

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
Add bitmap	Unsigned Short	A bitmap which specifies which sections need add information because of very high block ids. not yet used

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	Field Name	Field Type	Notes
0x27	X	Float
	Y	Float
	Z	Float
	Radius	Float	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

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 effects 1013 and 1018 (mob.wither.spawn and mob.enderdragon.end, respectively), 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.
	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	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.
2005	Spawn fall particles (when player hits ground). Data fall damage taken for particle speed

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.

All known sound effect names can be seen here.

Custom sounds made be added by resource packs

Packet ID	Field Name	Field Type	Notes
0x29	Sound name	String
	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	Field Name	Field Type	Notes
0x2A	Particle name	String	The name of the particle to create. A list can be found here
	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

Change Game State

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

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	Notes
0x2B	Reason	Unsigned Byte
	Value	Float	Depends on reason

Reason codes

Code	Effect	Notes
0	Invalid Bed	"tile.bed.notValid"
1	End raining
2	Begin raining
3	Change game mode	"gameMode.changed" 0 - Survival, 1 - Creative, 2 - Adventure
4	Enter credits
5	Demo messages	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

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	Field Name	Field Type	Notes
0x2C	Entity ID	VarInt	The entity ID 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	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	Unsigned Byte	The window type to use for display. Check below
	Window title	String	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).
	Use provided window title	Bool	If false, the client will look up a string like "window.minecart". If true, the client uses what the server provides.
	Entity ID	Int	EntityHorse's entityId. Only sent when window type is equal to 11 (AnimalChest).

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 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	Notes
0x2E	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	Field Name	Field Type	Notes
0x2F	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 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	Notes
0x30	Window ID	Unsigned Byte	The id of window which items are being sent for. 0 for player inventory.
	Count	Short	The number of slots (see below)
	Slot data	Array of Slots

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

Window Property

Packet ID	Field Name	Field Type	Notes
0x31	Window ID	Unsigned Byte	The id of the window.
	Property	Short	Which property should be updated.
	Value	Short	The new value for the property.

Furnace

Properties:

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

Values:

• 0-200 for progress arrow
• 0-200 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.

Beacon

• 0: Power level
• 1: Potion effect one
• 2: Potion effect two

Anvil

• 0: Maximum cost

Brewing Stand

• 0: Brew time

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). 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	Notes
0x32	Window ID	Unsigned 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	Bool	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	Field Name	Field Type	Notes
0x33	X	Int	Block X Coordinate
	Y	Short	Block Y Coordinate
	Z	Int	Block Z Coordinate
	Line 1	String	First line of text in the sign
	Line 2	String	Second line of text in the sign
	Line 3	String	Third line of text in the sign
	Line 4	String	Fourth line of text in the sign

Maps

If the first byte of the array 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 array 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.

If the first byte of the array is 2, the second byte is the map scale.

Packet ID	Field Name	Field Type	Notes
0x34	Item Damage	VarInt	The damage value of the map being modified
	Length	Short	Length of following byte array
	Data	Byte Array	Array data

Update Block Entity

Essentially a block update on a block entity.

Packet ID	Field Name	Field Type	Notes
0x35	X	Int
	Y	Short
	Z	Int
	Action	Unsigned Byte	The type of update to perform
	Data length	Short	Varies
	NBT Data	Byte Array	Present if data length > 0. Compressed with gzip. 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	X	Int	X in block coordinates
	Y	Int	Y in block coordinates
	Z	Int	Z in block coordinates

Statistics

Packet ID	Field Name		Field Type	Notes
0x37	Count		VarInt	Number of entrys
	Entry	Statistic's name	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	Field Name	Field Type	Notes
0x38	Player name	String	Supports chat colouring, limited to 16 characters.
	Online	Bool	The client will remove the user from the list if false.
	Ping	Short	Ping, presumably in ms.

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	Field Name	Field Type	Notes
0x39	Flags	Byte
	Flying speed	Float	previous integer value divided by 250
	Walking speed	Float	previous integer value divided by 250

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	Field Name	Field Type	Notes
0x3A	Count	VarInt	Number of following strings
	Match	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 or remove one.

Packet ID	Field Name	Field Type	Notes
0x3B	Objective name	String	An unique name for the objective
	Objective value	String	The text to be displayed for the score.
	Create/Remove	Byte	0 to create the scoreboard. 1 to remove the scoreboard. 2 to update the display text.

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	Int	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

Display Scoreboard

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

Packet ID	Field Name	Field Type	Notes
0x3D	Position	Byte	The position of the scoreboard. 0 = list, 1 = sidebar, 2 = belowName.
	Score Name	String	The unique name for the scoreboard to be displayed.

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
	Player count	Short	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.

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	Field Name	Field Type	Notes
0x3F	Channel	String	Name of the "channel" used to send the data.
	Length	Short	Length of the following byte array
	Data	Byte Array	Any data.

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	Field Name	Field Type	Notes
0x40	Reason	String	Displayed to the client when the connection terminates. Must be valid JSON.

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	Int

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.

For more information, see Chat.

Packet ID	Field Name	Field Type	Notes
0x01	Message	String

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	Int
	Mouse	Byte	0 = Right-click, 1 = Left-click

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	Field Name	Field Type	Notes
0x03	On Ground	Bool	True if the client is on the ground, False otherwise

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…
	HeadY	Double	Absolute head position
	Z	Double	Absolute position
	On Ground	Bool	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

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	Notes
0x05	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 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…
	HeadY	Double	Absolute head position
	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)
	X	Int	Block position
	Y	Unsigned Byte	Block position
	Z	Int	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	X	Int	Block position
	Y	Unsigned Byte	Block position
	Z	Int	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.

Held Item Change

Sent when the player changes the slot selection

Packet ID	Field Name	Field Type	Notes
0x09	Slot	Short	The slot which the player has selected (0-8)

Animation

Packet ID	Field Name	Field Type	Notes
0x0A	Entity ID	Int	Player ID
	Animation	Byte	Animation ID

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
6	Critical effect
7	Magic critical effect
102	(unknown)
104	Crouch
105	Uncrouch

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	Int	Player ID
	Action ID	Byte	The ID of the action, see below.
	Jump Boost	Int	Horse jump boost. Ranged from 0 -> 100.

Action ID can be one of the following values:

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

Steer Vehicle

Packet ID	Field Name	Field Type	Notes
0x0C	Sideways	Float	Positive to the left of the player
	Forward	Float	Positive forward
	Jump	Bool
	Unmount	Bool	True when leaving the vehicle

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	Field Name	Field Type	Notes
0x0D	Window id	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	Field Name	Field Type	Notes
0x0E	Window ID	Byte	The id of the window which was clicked. 0 for player inventory.
	Slot	Short	The clicked slot. See below.
	Button	Byte	The button used in the click. See below.
	Action number	Short	A unique number for the action, used for transaction handling (See the Transaction packet).
	Mode	Byte	Inventory operation mode. See below.
	Clicked item	Slot

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.

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)
	1	Normal	Ctrl + Drop key (Ctrl-Q)
	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 items), then holding mouse button (left, right or middle) and dragging holded 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.

Confirm Transaction

Packet ID	Field Name	Field Type	Notes
0x0F	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	Bool	Whether the action was accepted.

Creative Inventory Action

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	Notes
0x10	Slot	Short	Inventory slot
	Clicked item	Slot

Enchant Item

Packet ID	Field Name	Field Type	Notes
0x11	Window ID	Byte	The ID 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	Field Name	Field Type	Notes
0x12	X	Int	Block X Coordinate
	Y	Short	Block Y Coordinate
	Z	Int	Block Z Coordinate
	Line 1	String	First line of text in the sign
	Line 2	String	Second line of text in the sign
	Line 3	String	Third line of text in the sign
	Line 4	String	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 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. 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	Notes
0x13	Flags	Byte
	Flying speed	Float	previous integer value divided by 250
	Walking speed	Float	previous integer value divided by 250

Tab-Complete

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

Packet ID	Field Name	Field Type	Notes
0x14	Text	String

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
	Difficulty	Byte	Client-side difficulty from options.txt
	Show Cape	Bool	Client-side "show cape" option

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	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	Field Name	Field Type	Notes
0x17	Channel	String	Name of the "channel" used to send the data.
	Length	Short	Length of the following byte array
	Data	Byte Array	Any data.

Status

The status ping works as follows.

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

Clientbound

Response

Packet ID	Field Name	Field Type	Notes
0x00	JSON Response	String	https://gist.github.com/thinkofdeath/6927216

Ping

Packet ID	Field Name	Field Type	Notes
0x01	Time	Long	Should be the same as sent by the client

Serverbound

Request

Packet ID	Field Name	Field Type	Notes
0x00

Ping

Packet ID	Field Name	Field Type	Notes
0x01	Time	Long

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.

* It could be that only one of the two conditions is enough for an unencrypted connection.

See Protocol Encryption for details.

Clientbound

Disconnect

Packet ID	Field Name	Field Type	Notes
0x00	JSON Data	String

Encryption Request

Packet ID	Field Name	Field Type	Notes
0x01	Server ID	String
	Length	Short	length of public key
	Public Key	Byte array
	Length	Short	length of verify token
	Verify Token	Byte array

See Protocol Encryption for details.

Login Success

Packet ID	Field Name	Field Type	Notes
0x02	UUID	String
	Username	String

Serverbound

Login Start

Packet ID	Field Name	Field Type	Notes
0x00	Name	String

Encryption Response

Packet ID	Field Name	Field Type	Notes
0x01	Length	Short	length of public key
	Shared Secret	Byte array
	Length	Short	length of verify token
	Verify Token	Byte array

See Protocol Encryption for details.

See Also

• Data Types
• Protocol History
• Units of Measurement