Pre-release protocol

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This page documents the changes from the last stable Minecraft release (currently 1.12.2, protocol 340) to the current pre-release (currently 17w47b, protocol 347). 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
0x07 Statistics Current Pre
0x0F 0x0E Chat Message (clientbound) Current (unchanged)
0x10 0x0F Multi Block Change Current (unchanged)
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 (unchanged)
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 (unchanged)
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)
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

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

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

Tab-Complete (clientbound)

Huh.png 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

Huh.png 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
Huh.png The following information needs to be added to this page:
This packet most likely did change with the flattening, but the exact changes are not known yet.

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).

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.

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

Serverbound

Tab-Complete (serverbound)

Huh.png 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.

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 340 347)
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.