Pre-release protocol

This page documents the changes from the last stable Minecraft release (currently 1.12.2, protocol 340) to the current pre-release (currently 17w45a, protocol 343). Note that this page contains bleeding-edge information that may not be completely or correctly documented.

One 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 occurred to the respective packets there.

Contents

Data types

No changes so far.

Packets

ID	Packet name	Documentation
Handshaking serverbound
0x00	Handshake	Current	Pre
Play clientbound
0x0E	Tab-Complete (clientbound)	Current
0x0F 0x0E	Chat Message (clientbound)	Current	(unchanged)
0x10 0x0F	Multi Block Change	Current	(unchanged)
0x10	Declare commands		Pre
0x19	Named Sound Effect	Current	Pre
0x22	Particle	Current	Pre
0x49	Stop sound		Pre
0x49 0x4A	Sound Effect	Current	(unchanged)
0x4A 0x4B	Player List Header And Footer	Current	(unchanged)
0x4B 0x4C	Collect Item	Current	(unchanged)
0x4C 0x4D	Entity Teleport	Current	(unchanged)
0x4D 0x4E	Advancements	Current	(unchanged)
0x4E 0x4F	Entity Properties	Current	(unchanged)
0x4F 0x50	Entity Effect	Current	(unchanged)
Play clientbound
0x01	Tab-Complete (serverbound)	Current
0x02 0x01	Chat Message (serverbound)	Current	(unchanged)
0x03 0x02	Client Status	Current	(unchanged)
0x04 0x03	Client Settings	Current	(unchanged)
0x05 0x04	Confirm Transaction (serverbound)	Current	(unchanged)
0x06 0x05	Enchant Item	Current	(unchanged)
0x07 0x06	Click Window	Current	(unchanged)
0x08 0x07	Close Window (serverbound)	Current	(unchanged)
0x09 0x08	Plugin Message (serverbound)	Current	(unchanged)
0x0A 0x09	Use Entity	Current	(unchanged)
0x0B 0x0A	Keep Alive (serverbound)	Current	(unchanged)
0x0C 0x0B	Player	Current	(unchanged)
0x0D 0x0C	Player Position	Current	(unchanged)
0x0E 0x0D	Player Position And Look (serverbound)	Current	(unchanged)
0x0F 0x0E	Player Look	Current	(unchanged)
0x10 0x0F	Vehicle Move (serverbound)	Current	(unchanged)
0x11 0x10	Steer Boat	Current	(unchanged)
0x12 0x11	Craft Recipe Request	Current	(unchanged)
0x13 0x12	Player Abilities (serverbound)	Current	(unchanged)
0x14 0x13	Player Digging	Current	(unchanged)
0x15 0x14	Entity Action	Current	(unchanged)
0x16 0x15	Steer Vehicle	Current	(unchanged)
0x17 0x16	Crafting Book Data	Current	(unchanged)
0x18 0x17	Resource Pack Status	Current	(unchanged)
0x19 0x18	Advancement Tab	Current	(unchanged)
0x1A 0x19	Held Item Change (serverbound)	Current	(unchanged)
0x1B 0x1A	Creative Inventory Action	Current	(unchanged)
0x1C 0x1B	Update Sign	Current	(unchanged)
0x1D 0x1C	Animation (serverbound)	Current	(unchanged)
0x1E 0x1D	Spectate	Current	(unchanged)
0x1F 0x1E	Player Block Placement	Current	(unchanged)
0x20 0x1F	Use Item	Current	(unchanged)

New/modified data types

No changes so far.

Block Actions

No changes so far.

Plugin Channels

MC|StopSound

Server to client

Used to implement the /stopsound command. Stops a sound that is currently playing on the client.

Field name	Field type	Notes
Sound category	String	Should be one of the sound categories used in Named Sound Effect, but if it's invalid or empty then it is (intentionally) treated as all sound categories.
Sound name	String	A sound effect name. If left empty, all sounds are stopped.

Emptiness of sound category or sound name can be combined, IE a empty sound name but a set sound category will stop all sounds in the given category.

This plugin channel has been replaced by the stop sound packet.

Play

Clientbound

Declare commands

Currently has no payload, but will serialize a Brigadier RootCommandNode instance.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x10	Play	Client	no fields

Named Sound Effect

See also: #Sound Effect

Used to play a sound effect on the client. Custom sounds may be added by resource packs.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x19	Play	Client	Sound Name	String (256) Identifier	All sound effect names as of 1.12.2 can be seen here.
			Sound Category	VarInt Enum	The category that this sound will be played from (current categories)
			Effect Position X	Int	Effect X multiplied by 8 (fixed-point number with only 3 bits dedicated to the fractional part)
			Effect Position Y	Int	Effect Y multiplied by 8 (fixed-point number with only 3 bits dedicated to the fractional part)
			Effect Position Z	Int	Effect Z multiplied by 8 (fixed-point number with only 3 bits dedicated to the fractional part)
			Volume	Float	1 is 100%, can be more
			Pitch	Float	Float between 0.5 and 2.0 by Notchian clients

Particle

Displays the named particle

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x22	Play	Client	Particle ID	Int	See below
			Long Distance	Boolean	If true, particle distance increases from 256 to 65536
			X	Float	X position of the particle
			Y	Float	Y position of the particle
			Z	Float	Z position of the particle
			Offset X	Float	This is added to the X position after being multiplied by random.nextGaussian()
			Offset Y	Float	This is added to the Y position after being multiplied by random.nextGaussian()
			Offset Z	Float	This is added to the Z position after being multiplied by random.nextGaussian()
			Particle Data	Float	The data of each particle
			Particle Count	Int	The number of particles to create
			Data	Array of VarInt Varies	Length depends on particle. "iconcrack" has length of 2, "blockcrack", "blockdust", and "fallingdust" have lengths of 1, the rest have 0. Type of data varies based off of the particle. For "iconcrack", it is a Slot. For "blockcrack", "blockdust", and "fallingdust", it is a block state encoded as a VarInt that is an index within the global palette.

Stop sound

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x49	Play	Client	Flags	Byte	Controls which fields are present.
			Source	Optional VarInt enum	Only if flags is 3 or 1. See below. If not present, then sounds from all sources are cleared.
			Sound	Optional Identifier	Only if flags is 2 or 3. A sound effect name, see Named Sound Effect. If not present, then all sounds are cleared.

Categories:

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

Serverbound

No changes so far.

Handshaking

Clientbound

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

Serverbound

Handshake

This causes the server to switch into the target state.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x00	Handshaking	Server	Protocol Version	VarInt	See protocol version numbers (currently 340 343)
			Server Address	String	Hostname or IP, e.g. localhost or 127.0.0.1, that was used to connect. The Notchian server does not use this information.
			Server Port	Unsigned Short	Default is 25565. The Notchian server does not use this information.
			Next State	VarInt Enum	1 for status, 2 for login

Status

Clientbound

No changes so far.

Serverbound

No changes so far.

Login

Clientbound

No changes so far.

Serverbound

No changes so far.