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 17w48a, protocol 348). 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

Other definitions

Global palette

A table/dictionary/palette mapping nonnegative integers to block states. The block state IDs can be constructed from this table by multiplying what the Minecraft Wiki calls “block IDs” by 16 and adding the metadata/damage value (or in most programming languages block_id << 4 | metadata). Block state IDs are created in a linear fashion based off of order of assignment. More information soon.

Packets

ID	Packet name	Documentation
Handshaking serverbound
0x00	Handshake	Current	Pre
Play clientbound
0x07	Statistics	Current	Pre
0x0B	Block Change	Current	Pre
0x0F 0x0E	Chat Message (clientbound)	Current	(unchanged)
0x10 0x0F	Multi Block Change	Current	Pre
0x0E 0x10	Tab-Complete (clientbound)	Current	Pre
0x11	Declare Commands		Pre
0x11 0x12	Confirm Transaction (clientbound)	Current	(unchanged)
0x12 0x13	Close Window (clientbound)	Current	(unchanged)
0x13 0x14	Open Window	Current	(unchanged)
0x14 0x15	Window Items	Current	(unchanged)
0x15 0x16	Window Property	Current	(unchanged)
0x16 0x17	Set Slot	Current	(unchanged)
0x17 0x18	Set Cooldown	Current	(unchanged)
0x18 0x19	Plugin Message (clientbound)	Current	(unchanged)
0x19 0x1A	Named Sound Effect	Current	Pre
0x1A 0x1B	Disconnect (play)	Current	(unchanged)
0x1B 0x1C	Entity Status	Current	(unchanged)
0x1C 0x1D	Explosion	Current	(unchanged)
0x1D 0x1E	Unload Chunk	Current	(unchanged)
0x1E 0x1F	Change Game State	Current	(unchanged)
0x1F 0x20	Keep Alive (clientbound)	Current	(unchanged)
0x20 0x21	Chunk Data	Current	Pre
0x21 0x22	Effect	Current	(unchanged)
0x22 0x23	Particle	Current	Pre
0x23 0x24	Join Game	Current	(unchanged)
0x24 0x25	Map	Current	(unchanged)
0x25 0x26	Entity	Current	(unchanged)
0x26 0x27	Entity Relative Move	Current	(unchanged)
0x27 0x28	Entity Look And Relative Move	Current	(unchanged)
0x28 0x29	Entity Look	Current	(unchanged)
0x29 0x2A	Vehicle Move (clientbound)	Current	(unchanged)
0x2A 0x2B	Open Sign Editor	Current	(unchanged)
0x2B 0x2C	Craft Recipe Response	Current	Pre
0x2C 0x2D	Player Abilities (clientbound)	Current	(unchanged)
0x2D 0x2E	Combat Event	Current	(unchanged)
0x2E 0x2F	Player List Item	Current	(unchanged)
0x2F 0x30	Player Position And Look (clientbound)	Current	(unchanged)
0x30 0x31	Use Bed	Current	(unchanged)
0x31 0x32	Unlock Recipes	Current	Pre
0x32 0x33	Destroy Entities	Current	(unchanged)
0x33 0x34	Remove Entity Effect	Current	(unchanged)
0x34 0x35	Resource Pack Send	Current	(unchanged)
0x35 0x36	Respawn	Current	(unchanged)
0x36 0x37	Entity Head Look	Current	(unchanged)
0x37 0x38	Select Advancement Tab	Current	(unchanged)
0x38 0x39	World Border	Current	(unchanged)
0x39 0x3A	Camera	Current	(unchanged)
0x3A 0x3B	Held Item Change (clientbound)	Current	(unchanged)
0x3B 0x3C	Display Scoreboard	Current	(unchanged)
0x3C 0x3D	Entity Metadata	Current	(unchanged)
0x3D 0x3E	Attach Entity	Current	(unchanged)
0x3E 0x3F	Entity Velocity	Current	(unchanged)
0x3F 0x40	Entity Equipment	Current	(unchanged)
0x40 0x41	Set Experience	Current	(unchanged)
0x41 0x42	Update Health	Current	(unchanged)
0x42 0x43	Scoreboard Objective	Current	(unchanged)
0x43 0x44	Set Passengers	Current	(unchanged)
0x44 0x45	Teams	Current	(unchanged)
0x45 0x46	Update Score	Current	(unchanged)
0x46 0x47	Spawn Position	Current	(unchanged)
0x47 0x48	Time Update	Current	(unchanged)
0x48 0x49	Title	Current	(unchanged)
0x4A	Stop Sound		Pre
0x49 0x4B	Sound Effect	Current	(unchanged)
0x4A 0x4C	Player List Header And Footer	Current	(unchanged)
0x4B 0x4D	Collect Item	Current	(unchanged)
0x4C 0x4E	Entity Teleport	Current	(unchanged)
0x4D 0x4F	Advancements	Current	(unchanged)
0x4E 0x50	Entity Properties	Current	(unchanged)
0x4F 0x51	Entity Effect	Current	(unchanged)
0x52	Unknown		Pre
Play serverbound
0x02 0x01	Chat Message (serverbound)	Current	(unchanged)
0x03 0x02	Client Status	Current	(unchanged)
0x04 0x03	Client Settings	Current	(unchanged)
0x01 0x04	Tab-Complete (serverbound)	Current	Pre
0x12	Craft Recipe Request	Current	Pre

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

Block Change

Fired whenever a block is changed within the render distance.

Changing a block in a chunk that is not loaded is not a stable action. The Notchian client currently uses a shared empty chunk which is modified for all block changes in unloaded chunks; while in 1.9 this chunk never renders in older versions the changed block will appear in all copies of the empty chunk. Servers should avoid sending block changes in unloaded chunks and clients should ignore such packets.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x0B	Play	Client	Location	Position	Block Coordinates
			Block ID	VarInt	The new block state ID for the block as given in the global palette. (When reading data: type = id >> 4, meta = id & 15, when writing data: id = type << 4 | (meta & 15)) See that section for more information.

Statistics

Sent as a response to Client Status (id 1).

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x07	Play	Client	Count		VarInt		Number of elements in the following array
			Statistic	Name	Array	String (32767)	https://gist.github.com/Alvin-LB/8d0d13db00b3c00fd0e822a562025eff
				Unknown 1		VarInt
				Unknown 2		VarInt
				Value		VarInt	The amount to set it to

Multi Block Change

Fired whenever 2 or more blocks are changed within the same chunk on the same tick.

Changing blocks in chunks not loaded by the client is unsafe (see note on Block Change).

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x10 0x0F	Play	Client	Chunk X		Int		Chunk X coordinate
			Chunk Z		Int		Chunk Z coordinate
			Record Count		VarInt		Number of elements in the following array, i.e. the number of blocks affected
			Record	Horizontal Position	Array	Unsigned Byte	The 4 most significant bits (0xF0) encode the X coordinate, relative to the chunk. The 4 least significant bits (0x0F) encode the Z coordinate, relative to the chunk.
				Y Coordinate		Unsigned Byte	Y coordinate of the block
				Block ID		VarInt	The new block state ID for the block as given in the global palette. (When reading data: type = id >> 4, meta = id & 15, when writing data: id = type << 4 | (meta & 15)) See that section for more information.

To decode the position into a world position:

worldX = (horizPos >> 4 & 15) + (chunkX * 16);
worldY = vertPos;
worldZ = (horizPos & 15) + (chunkZ * 16);

Tab-Complete (clientbound)

	The following information needs to be added to this page:
	This is most definitely no longer an accurate description of this packet

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. The client sorts these alphabetically before listing them.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x0E 0x10	Play	Client	Transaction Id	VarInt	This id should also be used in the tab completion response packet, or it will be ignored.
			Start	VarInt
			Length	VarInt
			Count	VarInt	Number of elements in the following array
			Matches	Array of String (32767)	One eligible command, note that each command is sent separately instead of in a single string, hence the need for Count

Declare Commands

	The following information needs to be added to this page:
	This information is probably incomplete/inaccurate

Lists all of the commands on the server, and how they are parsed.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x11	Play	Client	Count	VarInt	Length of the following array
			Nodes	Array of Node	A array of CommandNodes
			Root index	VarInt	Index of the RootCommandNode in the previous array

Node:

Field Name	Field Type	Notes
Flags	Byte (read) and VarInt (written)	Writing as VarInt doesn't currently cause any problems because there aren't more then 7 bits used, but it's something to look out for (don't set more than the 7 lowest bits, or things will break). Bit mask Meaning 0x03 Type of the CommandNode 0 RootCommandNode 1 LiteralCommandNode 2 ArgumentCommandNode 0x04 Has command 0x08 Has redirect node 0x10 Has custom suggestions, currently only present if the type is a ArgumentCommandNode
Children Count	VarInt	Length of the following array
Children	Array of VarInt	The indexes of the children CommandNodes within the Nodes array
Redirect node	Optional VarInt	Only if flags & 0x08. Points to the redirect CommandNode within the Nodes array
Extra node data	Extra node data	Type depends on the CommandNode type, see below.

Extra node data:

Type	Field Name	Field Type	Notes
RootCommandNode	Empty	Empty
LiteralCommandNode	Literal	String (32767)	The text
ArgumentCommandNode	Name	String (32767)	The name of the argument
	Parser	Identifier	One of several known to the client, listed below. If the client does not know the parser, reading this RequiredArgumentBuilder stops immediately (following fields are not read)
	Properties	Optional, varies	See below. Varies depending on the parser.
	Suggests	Optional Identifier	Only present if (flags & 0x10) != 0. See below for the available types.

Parsers:

Identifier	Description	Properties
brigadier:bool	Boolean value (true or false, case-sensitive)	None
brigadier:double	Double	Specifies min and max values: Name Type Description Flags Byte Min Optional double Only if flags & 0x01. If not specified, defaults to -Double.MAX_VALUE (≈ -1.7976931348623157E307) Max Optional double Only if flags & 0x02. If not specified, defaults to Double.MAX_VALUE (≈ 1.7976931348623157E307)
brigadier:float	Float	Specifies min and max values: Name Type Description Flags Byte Min Optional float Only if flags & 0x01. If not specified, defaults to -Float.MAX_VALUE (≈ -3.4028235E38) Max Optional float Only if flags & 0x02. If not specified, defaults to Float.MAX_VALUE (≈ 3.4028235E38)
brigadier:integer	Integer	Specifies min and max values: Name Type Description Flags Byte Min Optional integer Only if flags & 0x01. If not specified, defaults to Integer.MIN_VALUE (-2147483648) Max Optional integer Only if flags & 0x02. If not specified, defaults to Integer.MAX_VALUE (2147483647)
brigadier:string	A string	A VarInt enum: Value Name Description 0 SINGLE_WORD Reads a single word 1 QUOTABLE_PHRASE If it starts with a ", keeps reading until another " (allowing escaping with \). Otherwise behaves the same as SINGLE_WORD 2 GREEDY_PHRASE Reads the rest of the content after the cursor. Quotes will not be removed.
minecraft:entity	A selector, player name, or UUID.	Has a single flags byte: Bit mask Meaning 0x01 Only allows 1 entity/player 0x02 Only allows players
minecraft:game_profile	A player, online or not. Can also use a selector, which may match one or more players (but not entities).	None
minecraft:block_pos	A location, represented as 3 numbers (which must be integers). May use relative locations with ~.	None
minecraft:vec3	A location, represented as 3 numbers (which may have a decimal point, but will be moved to the center of a block if none is specified). May use relative locations with ~.	None
minecraft:vec2	A location, represented as 2 numbers (which may have a decimal point, but will be moved to the center of a block if none is specified). May use relative locations with ~.	None
minecraft:block	A block state, optionally including NBT and state information.	None
minecraft:item	An item, optionally including NBT.	None
minecraft:color	A chat color. One of the names from Chat#Colors, or reset. Case-insensitive.	None
minecraft:component	A JSON Chat component.	None
minecraft:message	A regular message, potentially including selectors.	None
minecraft:nbt	An NBT value, parsed using JSON-NBT rules.	None
minecraft:nbt_path	A path within an NBT value, allowing for array and member accesses.	None
minecraft:objective	A scoreboard objective.	None
minecraft:objective_criteria	A single score criterion.	None
minecraft:operation	A scoreboard operator	None
minecraft:particle	A particle effect (an identifier with extra information following it for specific particles, mirroring the Particle packet)	None
minecraft:rotation	An angle, represented as 2 numbers (which may have a decimal point, but will be moved to the center of a block if none is specified). May use relative locations with ~.	None
minecraft:scoreboard_slot	A scoreboard display position slot. list, sidebar, belowName, and sidebar.team.${color} for all chat colors (reset is not included)	None
minecraft:score_holder	Something that can join a team. Allows selectors and *.	Has a single flags byte: Bit mask Meaning 0x01 Unknown. 0x02 Unknown.
minecraft:swizzle	A collection of up to 3 axes.	None
minecraft:team	The name of a team. Parsed as an unquoted string.	None
minecraft:item_slot	A name for an inventory slot.	None
minecraft:resource_location	An Identifier.	None
minecraft:mob_effect	A potion effect.	None

Suggestion types:

Identifier	Description
minecraft:ask_server	Sends the Tab-Complete packet to the server to request tab completions.
minecraft:all_recipes	Suggests all the available recipes.
minecraft:available_sounds	Suggests all the available sounds.
minecraft:summonable_entities	Suggests all the summonable entities.

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 0x1A	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

Chunk Data

Main article: Chunk Format

See also: #Unload Chunk

The server only sends skylight information for chunk pillars in the Overworld, it's up to the client to know in which dimenison the player is currently located. You can also infer this information from the primary bitmask and the amount of uncompressed bytes sent. This packet also sends all block entities in the chunk (though sending them is not required; it is still legal to send them with Update Block Entity later).

Indexes into the global palette are still used, but since the global palette has changed, behavior is different.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x20 0x21	Play	Client	Chunk X	Int	Chunk coordinate (block coordinate divided by 16, rounded down)
			Chunk Z	Int	Chunk coordinate (block coordinate divided by 16, rounded down)
			Ground-Up Continuous	Boolean	See Chunk Format
			Primary Bit Mask	VarInt	Bitmask with bits set to 1 for every 16×16×16 chunk section whose data is included in Data. The least significant bit represents the chunk section at the bottom of the chunk column (from y=0 to y=15).
			Size	VarInt	Size of Data in bytes
			Data	Byte array	See data structure in Chunk Format
			Number of block entities	VarInt	Length of the following array
			Block entities	Array of NBT Tag	All block entities in the chunk. Use the x, y, and z tags in the NBT to determine their positions.

Particle

Displays the named particle

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x22 0x23	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.

Craft Recipe Response

Response to the serverbound packet (Craft Recipe Request), with the same recipe ID. Appears to be used to notify the UI.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x2B 0x2C	Play	Client	Window ID	Byte
			Recipe	VarInt Identifer	A recipe ID

Unlock Recipes

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x31 0x32	Play	Client
			Action	VarInt	0: init, 1: add, 2: remove
			Crafting Book Open	Boolean	If true, then the crafting book will be open when the player opens its inventory.
			Filtering Craftable	Boolean	If true, then the filtering option is active when the players opens its inventory.
			Array size 1	VarInt	Number of elements in the following array
			Recipe IDs	Array of VarInt Identifier
			Array size 2	Optional VarInt	Number of elements in the following array, only present if mode is 0 (init)
			Recipe IDs	Optional Array of VarInt Identifier, only present if mode is 0 (init)

Action:

• 0 (init) = All the recipes in the list 2 will added to the recipe book. All the recipes in list 1 will be tagged as displayed, recipes that aren't tagged will be shown in the notification. VERIFY LIST ORDER?
• 1 (add) = All the recipes in the list are added and their icon will be shown in the notification.
• 2 (remove) = Remove all the recipes in the list. This allows them to re-displayed when they are readded.

Recipe ID: These are hardcoded values in the client and server, all the recipe json files will be loaded in a specific order (alphabetical, like sounds) and internal ids will be assigned in that order. There are also inbuilt recipes like fireworks, banners, etc., these are the first recipes to have their id assigned. Due the fact that the recipes are loaded in a specific order will the ids very likely change when recipes get added. Custom recipes are scheduled for Minecraft 1.13, so most likely will things change a bit in that version.

Stop Sound

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x4A	Play	Client	Flags	Byte	Controls which fields are present.
			Source	Optional VarInt enum	Only if flags is 3 or 1 (bit mask 0x1). See below. If not present, then sounds from all sources are cleared.
			Sound	Optional Identifier	Only if flags is 2 or 3 (bit mask 0x2). 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

Unknown

ID 0x52. Probably declare recipes.

Serverbound

Tab-Complete (serverbound)

	The following information needs to be added to this page:
	This is most definitely no longer an accurate description of this packet

Sent when the user presses tab while writing text.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x01 0x04	Play	Server	Transaction Id	VarInt	The id received in the tab completion request packet, must match or the client will ignore this packet.
			Text	String (32767)	All text behind the cursor without the / (e.g. to the left of the cursor in left-to-right languages like English)
			Assume Command	Boolean	If true, the server will parse Text as a command even if it doesn't start with a /. Used in the command block GUI.
			Has Position	Boolean
			Looked At Block	Optional Position	The position of the block being looked at. Only sent if Has Position is true.

Craft Recipe Request

A replacement for Prepare Crafting Grid. It appears to behave more or less the same, but the client does not specify where to move the items.

This packet is sent when a player clicks a recipe in the crafting book that is craftable (white border).

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x12	Play	Server	Window ID	Byte
			Recipe	VarInt Identifier	A recipe ID
			Make all	Boolean	Affects the amount of items processed; true if shift is down when clicked

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 340 348)
			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.