Pre-release protocol

This page documents the changes from the last stable Minecraft release (currently 1.20.1, protocol 763) to the current pre-release (currently 1.20.2-pre1, protocol Snapshot 148). 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

NBT

Root NBT Tags are now always nameless. Below is an example of the resulting bytes from an encoded CompoundTag containing an IntTag(42) named test.

  0A 00 00 03 00 04 74 65 73 74 00 00 00 2A 00 | Before
  0A       03 00 04 74 65 73 74 00 00 00 2A 00 | Now

This affects all packets and data types containing NBT Tag fields:

• Chunk Data and Update Light Packet
• Block Entity Data Packet
• Entity Effect Packet
• Tag Query Response Packet
• Registry Data Packet
• Slot data type
• Metadata NBT type

Packets

ID	Packet name	Documentation
Login clientbound
0x02	Login Success	Current	Pre
Login serverbound
0x00	Login Start	Current	Pre
0x03	Login Acknowledged		Pre
Configuration clientbound
0x00	Plugin Message (configuration)		Pre
0x01	Disconnect (configuration)		Pre
0x02	Finish Configuration		Pre
0x03	Keep Alive (configuration)		Pre
0x04	Ping (configuration)		Pre
0x05	Registry Data		Pre
0x06	Resource Pack (configuration)		Pre
0x07	Feature Flags		Pre
0x08	Update Tags		Pre
Configuration serverbound
0x00	Client Information (configuration)		Pre
0x01	Plugin Message (configuration)		Pre
0x02	Finish Configuration		Pre
0x03	Keep Alive (configuration)		Pre
0x04	Pong (configuration)		Pre
0x05	Resource Pack		Pre
Play clientbound
0x0D	Chunk Batch Finished		Pre
0x0E	Chunk Batch Start		Pre
0x0D 0x0F	Chunk Biomes	Current	(unchanged)
0x0E 0x10	Clear Titles	Current	(unchanged)
0x0F 0x11	Command Suggestions Response	Current	(unchanged)
0x10 0x12	Commands	Current	(unchanged)
0x11 0x13	Close Container	Current	(unchanged)
0x12 0x14	Set Container Content	Current	(unchanged)
0x13 0x15	Set Container Property	Current	(unchanged)
0x14 0x16	Set Container Slot	Current	(unchanged)
0x15 0x17	Set Cooldown	Current	(unchanged)
0x16 0x18	Chat Suggestions	Current	(unchanged)
0x17 0x19	Plugin Message	Current	(unchanged)
0x18 0x1A	Damage Event	Current	(unchanged)
0x19 0x1B	Delete Message	Current	(unchanged)
0x1A 0x1C	Disconnect (play)	Current	(unchanged)
0x1B 0x1D	Disguised Chat Message	Current	(unchanged)
0x1C 0x1E	Entity Event	Current	(unchanged)
0x1D 0x1F	Explosion	Current	(unchanged)
0x1E 0x20	Unload Chunk	Current	(unchanged)
0x1F 0x21	Game Event	Current	(unchanged)
0x20 0x22	Open Horse Screen	Current	(unchanged)
0x21 0x23	Hurt Animation	Current	(unchanged)
0x22 0x24	Initialize World Border	Current	(unchanged)
0x23 0x25	Keep Alive	Current	(unchanged)
0x24 0x26	Chunk Data and Update Light	Current	(unchanged)
0x25 0x27	World Event	Current	(unchanged)
0x26 0x28	Particle	Current	(unchanged)
0x27 0x29	Update Light	Current	(unchanged)
0x28 0x2A	Login (play)	Current	Pre
0x29 0x2B	Map Data	Current	(unchanged)
0x2A 0x2C	Merchant Offers	Current	(unchanged)
0x2B 0x2D	Update Entity Position	Current	(unchanged)
0x2C 0x2E	Update Entity Position and Rotation	Current	(unchanged)
0x2D 0x2F	Update Entity Rotation	Current	(unchanged)
0x2E 0x30	Move Vehicle	Current	(unchanged)
0x2F 0x31	Open Book	Current	(unchanged)
0x30 0x32	Open Screen	Current	(unchanged)
0x31 0x33	Open Sign Editor	Current	(unchanged)
0x32 0x34	Ping (play)	Current	(unchanged)
0x35	Ping Response (play)		Pre
0x33 0x36	Place Ghost Recipe	Current	(unchanged)
0x34 0x37	Player Abilities	Current	(unchanged)
0x35 0x38	Player Chat Message	Current	(unchanged)
0x36 0x39	End Combat	Current	(unchanged)
0x37 0x3A	Enter Combat	Current	(unchanged)
0x38 0x3B	Combat Death	Current	(unchanged)
0x39 0x3C	Player Info Remove	Current	(unchanged)
0x3A 0x3D	Player Info Update	Current	(unchanged)
0x3B 0x3E	Look At	Current	(unchanged)
0x3C 0x3F	Synchronize Player Position	Current	(unchanged)
0x3D 0x40	Update Recipe Book	Current	(unchanged)
0x3E 0x41	Remove Entities	Current	(unchanged)
0x3F 0x42	Remove Entity Effect	Current	(unchanged)
0x40 0x43	Resource Pack	Current	(unchanged)
0x41 0x44	Respawn	Current	Pre
0x42 0x45	Set Head Rotation	Current	(unchanged)
0x43 0x46	Update Section Blocks	Current	(unchanged)
0x44 0x47	Select Advancements Tab	Current	(unchanged)
0x45 0x48	Server Data	Current	(unchanged)
0x46 0x49	Set Action Bar Text	Current	(unchanged)
0x47 0x4A	Set Border Center	Current	(unchanged)
0x48 0x4B	Set Border Lerp Size	Current	(unchanged)
0x49 0x4C	Set Border Size	Current	(unchanged)
0x4A 0x4D	Set Border Warning Delay	Current	(unchanged)
0x4B 0x4E	Set Border Warning Distance	Current	(unchanged)
0x4C 0x4F	Set Camera	Current	(unchanged)
0x4D 0x50	Set Held Item	Current	(unchanged)
0x4E 0x51	Set Center Chunk	Current	(unchanged)
0x4F 0x52	Set Render Distance	Current	(unchanged)
0x50 0x53	Set Default Spawn Position	Current	(unchanged)
0x51 0x54	Display Objective	Current	Pre
0x52 0x55	Set Entity Metadata	Current	(unchanged)
0x53 0x56	Link Entities	Current	(unchanged)
0x54 0x57	Set Entity Velocity	Current	(unchanged)
0x55 0x58	Set Equipment	Current	(unchanged)
0x56 0x59	Set Experience	Current	(unchanged)
0x57 0x5A	Set Health	Current	(unchanged)
0x58 0x5B	Update Objectives	Current	(unchanged)
0x59 0x5C	Set Passengers	Current	(unchanged)
0x5A 0x5D	Update Teams	Current	(unchanged)
0x5B 0x5E	Update Score	Current	(unchanged)
0x5C 0x5F	Set Simulation Distance	Current	(unchanged)
0x5D 0x60	Set Subtitle Text	Current	(unchanged)
0x5E 0x61	Update Time	Current	(unchanged)
0x5F 0x62	Set Title Text	Current	(unchanged)
0x60 0x63	Set Title Animation Times	Current	(unchanged)
0x61 0x64	Entity Sound Effect	Current	(unchanged)
0x62 0x65	Sound Effect	Current	(unchanged)
0x66	Start Configuration		Pre
0x63 0x67	Stop Sound	Current	(unchanged)
0x64 0x68	System Chat Message	Current	(unchanged)
0x65 0x69	Set Tab List Header And Footer	Current	(unchanged)
0x66 0x6A	Tag Query Response	Current	(unchanged)
0x67 0x6B	Pickup Item	Current	(unchanged)
0x68 0x6C	Teleport Entity	Current	(unchanged)
0x69 0x6D	Update Advancements	Current	Pre
0x6A 0x6E	Update Attributes	Current	(unchanged)
0x6B	Feature Flags	Current
0x6C 0x6F	Entity Effect	Current	(unchanged)
0x6D 0x70	Update Recipes	Current	(unchanged)
0x6E 0x71	Update Tags	Current	(unchanged)
Play serverbound
0x07	Chunk Batch Received		Pre
0x07 0x08	Client Command	Current	(unchanged)
0x08 0x09	Client Information	Current	(unchanged)
0x09 0x0A	Command Suggestions Request	Current	(unchanged)
0x0B	Configuration Acknowledged		Pre
0x0A 0x0C	Click Container Button	Current	(unchanged)
0x0B 0x0D	Click Container	Current	(unchanged)
0x0C 0x0E	Close Container	Current	(unchanged)
0x0D 0x0F	Plugin Message	Current	(unchanged)
0x0E 0x10	Edit Book	Current	(unchanged)
0x0F 0x11	Query Entity Tag	Current	(unchanged)
0x10 0x12	Interact	Current	(unchanged)
0x11 0x13	Jigsaw Generate	Current	(unchanged)
0x12 0x14	Keep Alive	Current	(unchanged)
0x13 0x15	Lock Difficulty	Current	(unchanged)
0x14 0x16	Set Player Position	Current	(unchanged)
0x15 0x17	Set Player Position and Rotation	Current	(unchanged)
0x16 0x18	Set Player Rotation	Current	(unchanged)
0x17 0x19	Set Player On Ground	Current	(unchanged)
0x18 0x1A	Move Vehicle	Current	(unchanged)
0x19 0x1B	Paddle Boat	Current	(unchanged)
0x1A 0x1C	Pick Item	Current	(unchanged)
0x1D	Ping Request (play)		Pre
0x1B 0x1E	Place Recipe	Current	(unchanged)
0x1C 0x1F	Player Abilities	Current	(unchanged)
0x1D 0x20	Player Action	Current	(unchanged)
0x1E 0x21	Player Command	Current	(unchanged)
0x1F 0x22	Player Input	Current	(unchanged)
0x20 0x23	Pong (play)	Current	(unchanged)
0x21 0x24	Change Recipe Book Settings	Current	(unchanged)
0x22 0x25	Set Seen Recipe	Current	(unchanged)
0x23 0x26	Rename Item	Current	(unchanged)
0x24 0x27	Resource Pack	Current	(unchanged)
0x25 0x28	Seen Advancements	Current	(unchanged)
0x26 0x29	Select Trade	Current	(unchanged)
0x27 0x2A	Set Beacon Effect	Current	(unchanged)
0x28 0x2B	Set Held Item	Current	(unchanged)
0x29 0x2C	Program Command Block	Current	(unchanged)
0x2A 0x2D	Program Command Block Minecart	Current	(unchanged)
0x2B 0x2E	Set Creative Mode Slot	Current	(unchanged)
0x2C 0x2F	Program Jigsaw Block	Current	(unchanged)
0x2D 0x30	Program Structure Block	Current	(unchanged)
0x2E 0x31	Update Sign	Current	(unchanged)
0x2F 0x32	Swing Arm	Current	(unchanged)
0x30 0x33	Teleport To Entity	Current	(unchanged)
0x31 0x34	Use Item On	Current	(unchanged)
0x32 0x35	Use Item	Current	(unchanged)

New/modified data types

No changes so far.

Entity Metadata

Display

Extends Entity.

Index	Type	Meaning		Default
8	VarInt	Interpolation delay		0
9	VarInt	Interpolation Duration		0
9	VarInt	Transformation interpolation duration		0
10	VarInt	Position/Rotation interpolation duration		0
10 11	Vector3	Translation		(0.0, 0.0, 0.0)
11 12	Vector3	Scale		(1.0, 1.0, 1.0)
12 13	Quaternion	Rotation left		(0.0, 0.0, 0.0, 1.0)
13 14	Quaternion	Rotation right		(0.0, 0.0, 0.0, 1.0)
14 15	Byte	Billboard Constraints (0 = FIXED, 1 = VERTICAL, 2 = HORIZONTAL, 3 = CENTER)		0
15 16	VarInt	Brightness override (blockLight << 4 | skyLight << 20)		-1
16 17	Float	View range		1.0
17 18	Float	Shadow radius		0.0
18 19	Float	Shadow strength		1.0
19 20	Float	Width		0.0
20 21	Float	Height		0.0
21 22	VarInt	Glow color override		-1

Block Display

Extends Display.

Index	Type	Meaning		Default
22 23	BlockID	Displayed block state		0 (Air)

Item Display

Extends Display.

Index	Type	Meaning		Default
22 23	Slot	Displayed item		Empty
23 24	Byte	Display type: 0 = NONE 1 = THIRD_PERSON_LEFT_HAND 2 = THIRD_PERSON_RIGHT_HAND 3 = FIRST_PERSON_LEFT_HAND 4 = FIRST_PERSON_RIGHT_HAND 5 = HEAD 6 = GUI 7 = GROUND 8 = FIXED		0 (NONE)

Text Display

Extends Display.

Index	Type	Meaning		Default
22 23	Chat	Text		Empty
23 24	VarInt	Line width		200
24 25	VarInt	Background color		1073741824 (0x40000000)
25 26	Byte	Text opacity		-1 (fully opaque)
26 27	Byte	Bit mask	Meaning	0
		0x01	Has shadow
		0x02	Is see through
		0x04	Use default background color
		0x08	Alignment: 0 = CENTER 1 or 3 = LEFT 2 = RIGHT

Block Actions

No changes so far.

Inventories

No changes so far.

Plugin Channels

No changes so far.

Play

Clientbound

Chunk Batch Finished

	The following information needs to be added to this page:
	Why does the formula uses 25 instead of the normal tick duration of 50?

Marks the end of a chunk batch. The Notchian client marks the time it receives this packet and calculates the ellapsed duration since the beggining of the chunk batch. The server uses this duration and the batch size received in this packet to estimate the number of milliseconds ellapsed per chunk received. This value is then used to calculate the desired number of chunks per tick through the formula 25 / millisPerChunk, which is reported to the server through Chunk Batch Received.

The Notchian client uses the samples from the latest 15 batches to estimate the milliseconds per chunk number.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x0D	Play	Client	Batch size	VarInt	Number of chunks.

Chunk Batch Start

Marks the start of a chunk batch. The Notchian client marks and stores the time it receives this packet.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x0E	Play	Client	no fields

Ping Response (play)

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x35	Play	Client	Payload	Long	Should be the same as sent by the client.

Login (play)

	The following information needs to be added to this page:
	Although the number of portal cooldown ticks is included in this packet, the whole portal usage process is still dictated entirely by the server. What kind of effect does this value have on the client, if any?

See Protocol Encryption for information on logging in.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x28 0x2A	Play	Client	Entity ID	Int	The player's Entity ID (EID).
			Is hardcore	Boolean
			Game mode	Unsigned Byte	0: Survival, 1: Creative, 2: Adventure, 3: Spectator.
			Previous Game mode	Byte	-1: Undefined (null), 0: Survival, 1: Creative, 2: Adventure, 3: Spectator. The previous game mode. Vanilla client uses this for the debug (F3 + N & F3 + F4) game mode switch. (More information needed)
			Dimension Count	VarInt	Size of the following array.
			Dimension Names	Array of Identifier	Identifiers for all dimensions on the server.
			Registry Codec	NBT Tag Compound	Represents certain registries that are sent from the server and are applied on the client.
			Dimension Type	Identifier	Name of the dimension type being spawned into.
			Dimension Name	Identifier	Name of the dimension being spawned into.
			Hashed seed	Long	First 8 bytes of the SHA-256 hash of the world's seed. Used client side for biome noise
			Max Players	VarInt	Was once used by the client to draw the player list, but now is ignored.
			View Distance	VarInt	Render distance (2-32).
			Simulation Distance	VarInt	The distance that the client will process specific things, such as entities.
			Reduced Debug Info	Boolean	If true, a Notchian client shows reduced information on the debug screen. For servers in development, this should almost always be false.
			Enable respawn screen	Boolean	Set to false when the doImmediateRespawn gamerule is true.
			Do limited crafting	Boolean	Whether players can only craft recipes they have already unlocked. Currently unused by the client.
			Dimension Type	Identifier	Name of the dimension type being spawned into.
			Dimension Name	Identifier	Name of the dimension being spawned into.
			Hashed seed	Long	First 8 bytes of the SHA-256 hash of the world's seed. Used client side for biome noise
			Game mode	Unsigned Byte	0: Survival, 1: Creative, 2: Adventure, 3: Spectator.
			Previous Game mode	Byte	-1: Undefined (null), 0: Survival, 1: Creative, 2: Adventure, 3: Spectator. The previous game mode. Vanilla client uses this for the debug (F3 + N & F3 + F4) game mode switch. (More information needed)
			Is Debug	Boolean	True if the world is a debug mode world; debug mode worlds cannot be modified and have predefined blocks.
			Is Flat	Boolean	True if the world is a superflat world; flat worlds have different void fog and a horizon at y=0 instead of y=63.
			Has death location	Boolean	If true, then the next two fields are present.
			Death dimension name	Optional Identifier	Name of the dimension the player died in.
			Death location	Optional Position	The location that the player died at.
			Portal cooldown	VarInt	The number of ticks until the player can use the portal again.

Respawn

	The following information needs to be added to this page:
	Although the number of portal cooldown ticks is included in this packet, the whole portal usage process is still dictated entirely by the server. What kind of effect does this value have on the client, if any?

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	State	Bound To	Field Name	Field Type	Notes
0x41 0x43	Play	Client	Dimension Type	Identifier	Valid dimensions are defined per dimension registry sent in Login (play)
			Dimension Name	Identifier	Name of the dimension being spawned into.
			Hashed seed	Long	First 8 bytes of the SHA-256 hash of the world's seed. Used client side for biome noise
			Game mode	Unsigned Byte	0: Survival, 1: Creative, 2: Adventure, 3: Spectator.
			Previous Game mode	Byte	-1: Undefined (null), 0: Survival, 1: Creative, 2: Adventure, 3: Spectator. The previous game mode. Vanilla client uses this for the debug (F3 + N & F3 + F4) game mode switch. (More information needed)
			Is Debug	Boolean	True if the world is a debug mode world; debug mode worlds cannot be modified and have predefined blocks.
			Is Flat	Boolean	True if the world is a superflat world; flat worlds have different void fog and a horizon at y=0 instead of y=63.
			Data kept	Byte	Bit mask. 0x01: Keep attributes, 0x02: Keep metadata. Tells which data should be kept on the client side once the player has respawned. In the Notchian implementation, this is context dependent: normal respawns (after death) keep no data; exiting the end poem/credits keeps the attributes; other dimension changes (portals or teleports) keep all data.
			Has death location	Boolean	If true, then the next two fields are present.
			Death dimension Name	Optional Identifier	Name of the dimension the player died in.
			Death location	Optional Position	The location that the player died at.
			Portal cooldown	VarInt	The number of ticks until the player can use the portal again.
			Data kept	Byte	Bit mask. 0x01: Keep attributes, 0x02: Keep metadata. Tells which data should be kept on the client side once the player has respawned. In the Notchian implementation, this is context dependent: normal respawns (after death) keep no data; exiting the end poem/credits keeps the attributes; other dimension changes (portals or teleports) keep all data.

Avoid changing player's dimension to same dimension they were already in unless they are dead. If you change the dimension to one they are already in, weird bugs can occur, such as the player being unable to attack other players in new world (until they die and respawn).

Before 1.16, if you must respawn a player in the same dimension without killing them, send two respawn packets, one to a different world and then another to the world you want. You do not need to complete the first respawn; it only matters that you send two packets.

Display Objective

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

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x51 0x53	Play	Client	Position	Byte VarInt	The position of the scoreboard. 0: list, 1: sidebar, 2: below name, 3 - 18: team specific sidebar, indexed as 3 + team color.
			Score Name	String (32767)	The unique name for the scoreboard to be displayed.

Start Configuration

Sent during gameplay in order to redo the configuration process. The client must respond with Configuration Acknowledged for the process to start.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x65	Play	Client	no fields

This packet switches the connection state to configuration.

Feature Flags

Used to enable and disable features, generally experimental ones, on the client.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x6B	Play	Client	Total Features	VarInt	Number of features that appear in the array below.
			Feature Flags	Identifier Array

Update Advancements

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x69 0x6D	Play	Client	Reset/Clear		Boolean		Whether to reset/clear the current advancements.
			Mapping size		VarInt		Size of the following array.
			Advancement mapping	Key	Array	Identifier	The identifier of the advancement.
				Value		Advancement	See below
			List size		VarInt		Size of the following array.
			Identifiers		Array of Identifier		The identifiers of the advancements that should be removed.
			Progress size		VarInt		Size of the following array.
			Progress mapping	Key	Array	Identifier	The identifier of the advancement.
				Value		Advancement progress	See below.

Advancement structure:

Field Name		Field Type		Notes
Has parent		Boolean		Indicates whether the next field exists.
Parent id		Optional Identifier		The identifier of the parent advancement.
Has display		Boolean		Indicates whether the next field exists.
Display data		Optional advancement display		See below.
Number of criteria		VarInt		Size of the following array.
Criteria	Key	Array	Identifier	The identifier of the criterion.
	Value		Void	There is no content written here. Perhaps this will be expanded in the future?
Array length		VarInt		Number of arrays in the following array.
Requirements	Array length 2	Array	VarInt	Number of elements in the following array.
	Requirement		Array of String (32767)	Array of required criteria.
Sends telemetry data		Boolean		Whether the client should include this achievement in the telemetry data when it's completed. The Notchian client only sends data for advancements on the minecraft namespace.

Advancement display:

Field Name	Field Type	Notes
Title	Chat
Description	Chat
Icon	Slot
Frame type	VarInt Enum	0 = task, 1 = challenge, 2 = goal.
Flags	Int	0x01: has background texture; 0x02: show_toast; 0x04: hidden.
Background texture	Optional Identifier	Background texture location. Only if flags indicates it.
X coord	Float
Y coord	Float

Advancement progress:

Field Name		Field Type		Notes
Size		VarInt		Size of the following array.
Criteria	Criterion identifier	Array	Identifier	The identifier of the criterion.
	Criterion progress		Criterion progress

Criterion progress:

Field Name	Field Type	Notes
Achieved	Boolean	If true, next field is present.
Date of achieving	Optional Long	As returned by Date.getTime.

Serverbound

Chunk Batch Received

Notifies the server that the chunk batch has been received by the client. The server uses the value sent in this packet to adjust the number of chunks to be sent in a batch.

The Notchian server will stop sending further chunk data until the client acknowledges the sent chunk batch. After the first acknowledgement, the server adjusts this number to allow up to 10 unacknowledged batches.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x07	Play	Server	Chunks per tick	Float	Desired chunks per tick.

Configuration Acknowledged

Sent by the client upon receiving a Start Configuration packet from the server.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x0B	Play	Server	no fields

This packet switches the connection state to configuration.

Ping Request (play)

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x1D	Play	Server	Payload	Long	May be any number. Notchian clients use a system-dependent time value which is counted in milliseconds.

Status

Clientbound

No changes so far.

Serverbound

No changes so far.

Login

Clientbound

Login Success

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x02	Login	Client	UUID		UUID
			Username		String (16)
			Number Of Properties		VarInt		Number of elements in the following array.
			Property	Name	Array	String (32767)
				Value		String (32767)
				Is Signed		Boolean
				Signature		Optional String (32767)	Only if Is Signed is true.

This packet switches the connection state to play configuration.

Serverbound

Login Start

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x00	Login	Server	Name	String (16)	Player's Username.
			Has Player UUID	Boolean	Whether or not the next field should be sent.
			Player UUID	Optional UUID	The UUID of the player logging in. Only sent if Has Player UUID is true.

Login Acknowledged

Acknowledgement to the Login Success packet sent by the server.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x03	Login	Server	no fields

Configuration

Clientbound

Plugin Message (configuration)

Main article: Plugin channels

Mods and plugins can use this to send their data. Minecraft itself uses several plugin channels. These internal channels are in the minecraft namespace.

More information on how it works on Dinnerbone's blog. More documentation about internal and popular registered channels are here.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x00	Configuration	Client	Channel	Identifier	Name of the plugin channel used to send the data.
			Data	Byte Array (1048576)	Any data. The length of this array must be inferred from the packet length.

In Notchian client, the maximum data length is 1048576 bytes.

Disconnect (configuration)

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x01	Configuration	Client	Reason	Chat	The reason why the player was disconnected.

Finish Configuration

Sent by the server to notify the client that the configuration process has finished. The client answers with its own Finish Configuration whenever it is ready to continue.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x02	Configuration	Client	no fields

This packet switches the connection state to play.

Keep Alive (configuration)

The server will frequently send out a keep-alive, each containing a random ID. The client must respond with the same payload (see serverbound Keep Alive). If the client does not respond to them for over 30 seconds, the server kicks the client. Vice versa, if the server does not send any keep-alives for 20 seconds, the client will disconnect and yields a "Timed out" exception.

The Notchian server uses a system-dependent time in milliseconds to generate the keep alive ID value.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x03	Configuration	Client	Keep Alive ID	Long

Ping (configuration)

Packet is not used by the Notchian server. When sent to the client, client responds with a Pong packet with the same id.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x04	Configuration	Client	ID	Int

Registry Data

Represents certain registries that are sent from the server and are applied on the client.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x05	Configuration	Client	Registry Codec	NBT Tag Compound	Information included below.

The Registry Codec NBT Tag Compound (Default value in JSON as of 1.19, 1.19.2, 1.20.1) includes three registries: "minecraft:dimension_type", "minecraft:worldgen/biome", and "minecraft:chat_type".

Name	Type	Notes
minecraft:dimension_type	TAG_Compound	The dimension type registry (see below).
minecraft:worldgen/biome	TAG_Compound	The biome registry (see below).
minecraft:chat_type	TAG_Compound	The chat type registry (see below).

Dimension type registry:

Name	Type	Notes
type	TAG_String	The name of the registry. Always "minecraft:dimension_type".
value	TAG_List	List of dimension types registry entries (see below).

Dimension type registry entry:

Name	Type	Notes
name	TAG_String	The name of the dimension type (for example, "minecraft:overworld").
id	TAG_Int	The protocol ID of the dimension (matches the index of the element in the registry list).
element	TAG_Compound	The dimension type (see below).

Dimension type:

Name	Type	Meaning		Values
piglin_safe	TAG_Byte	Whether piglins shake and transform to zombified piglins.		1: true, 0: false.
has_raids	TAG_Byte	Whether players with the Bad Omen effect can cause a raid.		1: true, 0: false.
monster_spawn_light_level	TAG_Int or TAG_Compound	Possibly the light level(s) at which monsters can spawn.	When TAG_Int, 0 - 15. When TAG_Compound, contains the fields: type (TAG_String), appears to be always "minecraft:uniform", and value (TAG_Compound), which contains the fields: max_inclusive (TAG_Int), min_inclusive (TAG_Int).
monster_spawn_block_light_limit	TAG_Int
natural	TAG_Byte	When false, compasses spin randomly. When true, nether portals can spawn zombified piglins.		1: true, 0: false.
ambient_light	TAG_Float	How much light the dimension has.		0.0 to 1.0.
fixed_time	Optional TAG_Long	If set, the time of the day is the specified value.		If set, 0 to 24000.
infiniburn	TAG_String	A resource location defining what block tag to use for infiniburn.		"#" or minecraft resource "#minecraft:...".
respawn_anchor_works	TAG_Byte	Whether players can charge and use respawn anchors.		1: true, 0: false.
has_skylight	TAG_Byte	Whether the dimension has skylight access or not.		1: true, 0: false.
bed_works	TAG_Byte	Whether players can use a bed to sleep.		1: true, 0: false.
effects	TAG_String	?		"minecraft:overworld", "minecraft:the_nether", "minecraft:the_end" or something else.
min_y	TAG_Int	The minimum Y level.		A multiple of 16. Example: -64
height	TAG_Int	The maximum height.		A multiple of 16. Example: 256
logical_height	TAG_Int	The maximum height to which chorus fruits and nether portals can bring players within this dimension. (Must be lower than height)		0-384.
coordinate_scale	TAG_Double	The multiplier applied to coordinates when traveling to the dimension.		0.00001 - 30000000.0
ultrawarm	TAG_Byte	Whether the dimensions behaves like the nether (water evaporates and sponges dry) or not. Also causes lava to spread thinner.		1: true, 0: false.
has_ceiling	TAG_Byte	Whether the dimension has a bedrock ceiling or not. When true, causes lava to spread faster.		1: true, 0: false.

Biome registry:

Name	Type	Notes
type	TAG_String	The name of the registry. Always "minecraft:worldgen/biome".
value	TAG_List	List of biome registry entries (see below).

Biome registry entry:

Name	Type	Notes
name	TAG_String	The name of the biome (for example, "minecraft:ocean").
id	TAG_Int	The protocol ID of the biome (matches the index of the element in the registry list).
element	TAG_Compound	The biome properties (see below).

Biome properties:

Name			Type		Meaning		Values
has_precipitation			TAG_Byte		Determines whether or not the biome has precipitation.		1: true, 0: false.
depth			Optional TAG_Float		The depth factor of the biome.		The default values vary between 1.5 and -1.8.
temperature			TAG_Float		The temperature factor of the biome.		The default values vary between 2.0 and -0.5.
scale			Optional TAG_Float		?		The default values vary between 1.225 and 0.0.
downfall			TAG_Float		?		The default values vary between 1.0 and 0.0.
category			Optional TAG_String		The category of the biome.		Known values are "ocean", "plains", "desert", "forest", "extreme_hills", "taiga", "swamp", "river", "nether", "the_end", "icy", "mushroom", "beach", "jungle", "mesa", "savanna", and "none".
temperature_modifier			Optional TAG_String		?		The only known value is "frozen".
effects	sky_color		TAG_Compound	TAG_Int	The color of the sky.		Example: 8364543, which is #7FA1FF in RGB.
	water_fog_color			TAG_Int	Possibly the tint color when swimming.		Example: 8364543, which is #7FA1FF in RGB.
	fog_color			TAG_Int	Possibly the color of the fog effect when looking past the view distance.		Example: 8364543, which is #7FA1FF in RGB.
	water_color			TAG_Int	The tint color of the water blocks.		Example: 8364543, which is #7FA1FF in RGB.
	foliage_color			Optional TAG_Int	The tint color of the grass.		Example: 8364543, which is #7FA1FF in RGB.
	grass_color			Optional TAG_Int	?		Example: 8364543, which is #7FA1FF in RGB.
	grass_color_modifier			Optional TAG_String	Unknown, likely affects foliage color.		If set, known values are "swamp" and "dark_forest".
	music			Optional TAG_Compound	Music properties for the biome.		If present, contains the fields: replace_current_music (TAG_Byte), sound (TAG_String), max_delay (TAG_Int), min_delay (TAG_Int).
	ambient_sound			Optional TAG_String	Ambient soundtrack.		If present, the ID of a soundtrack. Example: "minecraft:ambient.basalt_deltas.loop".
	additions_sound			Optional TAG_Compound	Additional ambient sound that plays randomly.		If present, contains the fields: sound (TAG_String), tick_chance (TAG_Double).
	mood_sound			Optional TAG_Compound	Additional ambient sound that plays at an interval.		If present, contains the fields: sound (TAG_String), tick_delay (TAG_Int), offset (TAG_Double), block_search_extent (TAG_Int).
	particle	probability	Optional TAG_Compound	TAG_FLOAT	Particles that appear randomly in the biome.	Possibly the probability of spawning the particle.	?
		options		TAG_COMPOUND		The properties of the particle to spawn.	Contains the field "type" (TAG_String), which identifies the particle type.

Chat registry:

Name	Type	Notes
type	TAG_String	The name of the registry. Always "minecraft:chat_type".
value	TAG_List	List of chat type registry entries (see below).

Chat type:

Name	Type	Notes
name	TAG_String	The type's name (eg "minecraft:chat")
id	TAG_Int
elements	TAG_Compound	"chat" and "narration" TAG_Compound's (see below)

Chat type "chat" and "narration":

Name	Type	Notes
translation_key	TAG_String
style	TAG_Compound	Similar to Chat JSON (only present in "chat" TAG_Compound)
parameters	TAG_List of TAG_String	Values can be "sender", "target" and "content"

Resource Pack

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x06	Configuration	Client	URL	String (32767)	The URL to the resource pack.
			Hash	String (40)	A 40 character hexadecimal and lowercase SHA-1 hash of the resource pack file. If it's not a 40 character hexadecimal string, the client will not use it for hash verification and likely waste bandwidth — but it will still treat it as a unique id
			Forced	Boolean	The notchian client will be forced to use the resource pack from the server. If they decline they will be kicked from the server.
			Has Prompt Message	Boolean	true If the next field will be sent false otherwise. When false, this is the end of the packet
			Prompt Message	Optional Chat	This is shown in the prompt making the client accept or decline the resource pack.

Feature Flags

Used to enable and disable features, generally experimental ones, on the client.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x07	Configuration	Client	Total Features	VarInt	Number of features that appear in the array below.
			Feature Flags	Identifier Array

As of 1.20.2, the following feature flags are available:

• minecraft:vanilla - enables vanilla features
• minecraft:bundle - enables support for the bundle
• minecraft:trade_rebalance - enables support for the rebalanced villager trades

Update Tags

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x08	Configuration	Client	Length of the array		VarInt
			Array of tags	Tag type	Array	Identifier	Tag identifier (Vanilla required tags are minecraft:block, minecraft:item, minecraft:fluid, minecraft:entity_type, and minecraft:game_event)
				Array of Tag		(See below)

Tags look like:

Field Name		Field Type		Notes
Length		VarInt		Number of elements in the following array
Tags	Tag name	Array	Identifier
	Count		VarInt	Number of elements in the following array
	Entries		Array of VarInt	Numeric ID of the given type (block, item, etc.).

More information on tags is available at: https://minecraft.gamepedia.com/Tag

And a list of all tags is here: https://minecraft.gamepedia.com/Tag#List_of_tags

Serverbound

Client Information (configuration)

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

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x00	Configuration	Server	Locale	String (16)	e.g. en_GB.
			View Distance	Byte	Client-side render distance, in chunks.
			Chat Mode	VarInt Enum	0: enabled, 1: commands only, 2: hidden. See processing chat for more information.
			Chat Colors	Boolean	“Colors” multiplayer setting. Can the chat be colored?
			Displayed Skin Parts	Unsigned Byte	Bit mask, see below.
			Main Hand	VarInt Enum	0: Left, 1: Right.
			Enable text filtering	Boolean	Enables filtering of text on signs and written book titles. Currently always false (i.e. the filtering is disabled)
			Allow server listings	Boolean	Servers usually list online players, this option should let you not show up in that list.

Displayed Skin Parts flags:

• Bit 0 (0x01): Cape enabled
• Bit 1 (0x02): Jacket enabled
• Bit 2 (0x04): Left Sleeve enabled
• Bit 3 (0x08): Right Sleeve enabled
• Bit 4 (0x10): Left Pants Leg enabled
• Bit 5 (0x20): Right Pants Leg enabled
• Bit 6 (0x40): Hat enabled

The most significant bit (bit 7, 0x80) appears to be unused.

Plugin Message (configuration)

Main article: Plugin channels

Mods and plugins can use this to send their data. Minecraft itself uses some plugin channels. These internal channels are in the minecraft namespace.

More documentation on this: https://dinnerbone.com/blog/2012/01/13/minecraft-plugin-channels-messaging/

Note that the length of Data is known only from the packet length, since the packet has no length field of any kind.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x00	Configuration	Server	Channel	Identifier	Name of the plugin channel used to send the data.
			Data	Byte Array (32767)	Any data, depending on the channel. minecraft: channels are documented here. The length of this array must be inferred from the packet length.

In Notchian server, the maximum data length is 32767 bytes.

Finish Configuration

Sent by the client to notify the client that the configuration process has finished. It is sent in response to the server's Finish Configuration.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x01	Configuration	Server	no fields

This packet switches the connection state to play.

Keep Alive (configuration)

The server will frequently send out a keep-alive (see clientbound Keep Alive), each containing a random ID. The client must respond with the same packet.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x02	Configuration	Server	Keep Alive ID	Long

Pong (configuration)

Response to the clientbound packet (Ping) with the same id.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x03	Configuration	Server	ID	Int	id is the same as the ping packet

Resource Pack (configuration)

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x04	Configuration	Server	Result	VarInt Enum	0: successfully loaded, 1: declined, 2: failed download, 3: accepted.