Pre-release protocol

This page documents the changes from the last stable Minecraft release (currently 1.20.4, protocol 765) to the current pre-release (currently 24w13a, protocol Snapshot 182). 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
Handshake serverbound
0x00	Handshake	Current	Pre
Login clientbound
0x01	Encryption Request	Current	Pre
0x05	Cookie Request (login)		Pre
Login serverbound
0x04	Cookie Response (login)		Pre
Configuration clientbound
0x00	Cookie Request (configuration)		Pre
0x00 0x01	Clientbound Plugin Message (configuration)	Current	(unchanged)
0x01 0x02	Disconnect (configuration)	Current	(unchanged)
0x02 0x03	Finish Configuration	Current	(unchanged)
0x03 0x04	Clientbound Keep Alive (configuration)	Current	(unchanged)
0x04 0x05	Ping (configuration)	Current	(unchanged)
0x06	Reset Chat		Pre
0x05 0x07	Registry Data	Current	Pre
0x06 0x08	Remove Resource Pack (configuration)	Current	(unchanged)
0x07 0x09	Add Resource Pack (configuration)	Current	(unchanged)
0x0A	Store Cookie (configuration)		Pre
0x0B	Transfer (configuration)		Pre
0x08 0x0C	Feature Flags	Current	(unchanged)
0x09 0x0D	Update Tags (configuration)	Current	(unchanged)
0x0E	Clientbound Known Packs		Pre
Configuration serverbound
0x01	Cookie Response (configuration)		Pre
0x01 0x02	Serverbound Plugin Message (configuration)	Current	(unchanged)
0x02 0x03	Finish Configuration	Current	(unchanged)
0x03 0x04	Serverbound Keep Alive (configuration)	Current	(unchanged)
0x04 0x05	Pong (configuration)	Current	(unchanged)
0x05 0x06	Resource Pack Response (configuration)	Current	(unchanged)
0x07	Serverbound Known Packs		Pre
Play clientbound
0x16	Cookie Request (Play)		Pre
0x16 0x17	Set Cooldown	Current	(unchanged)
0x17 0x18	Chat Suggestions	Current	(unchanged)
0x18 0x19	Clientbound Plugin Message (play)	Current	(unchanged)
0x19 0x1A	Damage Event	Current	(unchanged)
0x1B	Debug Sample		Pre
0x1A 0x1C	Delete Message	Current	(unchanged)
0x1B 0x1D	Disconnect (play)	Current	(unchanged)
0x1C 0x1E	Disguised Chat Message	Current	(unchanged)
0x1D 0x1F	Entity Event	Current	(unchanged)
0x1E 0x20	Explosion	Current	(unchanged)
0x1F 0x21	Unload Chunk	Current	(unchanged)
0x20 0x22	Game Event	Current	(unchanged)
0x21 0x23	Open Horse Screen	Current	(unchanged)
0x22 0x24	Hurt Animation	Current	(unchanged)
0x23 0x25	Initialize World Border	Current	(unchanged)
0x24 0x26	Clientbound Keep Alive (play)	Current	(unchanged)
0x25 0x27	Chunk Data and Update Light	Current	(unchanged)
0x26 0x28	World Event	Current	(unchanged)
0x27 0x29	Particle	Current	(unchanged)
0x28 0x2A	Update Light	Current	(unchanged)
0x29 0x2B	Login (play)	Current	Pre
0x2A 0x2C	Map Data	Current	(unchanged)
0x2B 0x2D	Merchant Offers	Current	(unchanged)
0x2C 0x2E	Update Entity Position	Current	(unchanged)
0x2D 0x2F	Update Entity Position and Rotation	Current	(unchanged)
0x2E 0x30	Update Entity Rotation	Current	(unchanged)
0x2F 0x31	Move Vehicle	Current	(unchanged)
0x30 0x32	Open Book	Current	(unchanged)
0x31 0x33	Open Screen	Current	(unchanged)
0x32 0x34	Open Sign Editor	Current	(unchanged)
0x33 0x35	Ping (play)	Current	(unchanged)
0x34 0x36	Ping Response (play)	Current	(unchanged)
0x35 0x37	Place Ghost Recipe	Current	(unchanged)
0x36 0x38	Player Abilities	Current	(unchanged)
0x37 0x39	Player Chat Message	Current	(unchanged)
0x38 0x3A	End Combat	Current	(unchanged)
0x39 0x3B	Enter Combat	Current	(unchanged)
0x3A 0x3C	Combat Death	Current	(unchanged)
0x3B 0x3D	Player Info Remove	Current	(unchanged)
0x3C 0x3E	Player Info Update	Current	(unchanged)
0x3D 0x3F	Look At	Current	(unchanged)
0x3E 0x40	Synchronize Player Position	Current	(unchanged)
0x3F 0x41	Update Recipe Book	Current	(unchanged)
0x40 0x42	Remove Entities	Current	(unchanged)
0x41 0x43	Remove Entity Effect	Current	(unchanged)
0x42 0x44	Reset Score	Current	(unchanged)
0x43 0x45	Remove Resource Pack (play)	Current	(unchanged)
0x44 0x46	Add Resource Pack (play)	Current	(unchanged)
0x45 0x47	Respawn	Current	Pre
0x46 0x48	Set Head Rotation	Current	(unchanged)
0x47 0x49	Update Section Blocks	Current	(unchanged)
0x48 0x4A	Select Advancements Tab	Current	(unchanged)
0x49 0x4B	Server Data	Current	(unchanged)
0x4A 0x4C	Set Action Bar Text	Current	(unchanged)
0x4B 0x4D	Set Border Center	Current	(unchanged)
0x4C 0x4E	Set Border Lerp Size	Current	(unchanged)
0x4D 0x4F	Set Border Size	Current	(unchanged)
0x4E 0x50	Set Border Warning Delay	Current	(unchanged)
0x4F 0x51	Set Border Warning Distance	Current	(unchanged)
0x50 0x52	Set Camera	Current	(unchanged)
0x51 0x53	Set Held Item	Current	(unchanged)
0x52 0x54	Set Center Chunk	Current	(unchanged)
0x53 0x55	Set Render Distance	Current	(unchanged)
0x54 0x56	Set Default Spawn Position	Current	(unchanged)
0x55 0x57	Display Objective	Current	(unchanged)
0x56 0x58	Set Entity Metadata	Current	(unchanged)
0x57 0x59	Link Entities	Current	(unchanged)
0x58 0x5A	Set Entity Velocity	Current	(unchanged)
0x59 0x5B	Set Equipment	Current	(unchanged)
0x5A 0x5C	Set Experience	Current	(unchanged)
0x5B 0x5D	Set Health	Current	(unchanged)
0x5C 0x5E	Update Objectives	Current	(unchanged)
0x5D 0x5F	Set Passengers	Current	(unchanged)
0x5E 0x60	Update Teams	Current	(unchanged)
0x5F 0x61	Update Score	Current	(unchanged)
0x60 0x62	Set Simulation Distance	Current	(unchanged)
0x61 0x63	Set Subtitle Text	Current	(unchanged)
0x62 0x64	Update Time	Current	(unchanged)
0x63 0x65	Set Title Text	Current	(unchanged)
0x64 0x66	Set Title Animation Times	Current	(unchanged)
0x65 0x67	Entity Sound Effect	Current	(unchanged)
0x66 0x68	Sound Effect	Current	(unchanged)
0x67 0x69	Start Configuration	Current	(unchanged)
0x68 0x6A	Stop Sound	Current	(unchanged)
0x6B	Store Cookie (Play)		Pre
0x69 0x6C	System Chat Message	Current	(unchanged)
0x6A 0x6D	Set Tab List Header And Footer	Current	(unchanged)
0x6B 0x6E	Tag Query Response	Current	(unchanged)
0x6C 0x6F	Pickup Item	Current	(unchanged)
0x6D 0x70	Teleport Entity	Current	(unchanged)
0x6E 0x71	Set Ticking State	Current	(unchanged)
0x6F 0x72	Step Tick	Current	(unchanged)
0x73	Transfer (Play)		Pre
0x70 0x74	Update Advancements	Current	(unchanged)
0x71 0x75	Update Attributes	Current	Pre
0x72 0x76	Entity Effect	Current	Pre
0x73 0x77	Update Recipes	Current	(unchanged)
0x74 0x78	Update Tags (play)	Current	(unchanged)
Play serverbound
0x04	Chat Command	Current	Pre
0x05	Signed Chat Command		Pre
0x05 0x06	Chat Message	Current	(unchanged)
0x06 0x07	Player Session	Current	(unchanged)
0x07 0x08	Chunk Batch Received	Current	(unchanged)
0x08 0x09	Client Status	Current	(unchanged)
0x09 0x0A	Client Information (play)	Current	(unchanged)
0x0A 0x0B	Command Suggestions Request	Current	(unchanged)
0x0B 0x0C	Acknowledge Configuration	Current	(unchanged)
0x0C 0x0D	Click Container Button	Current	(unchanged)
0x0D 0x0E	Click Container	Current	(unchanged)
0x0E 0x0F	Close Container	Current	(unchanged)
0x0F 0x10	Change Container Slot State	Current	(unchanged)
0x11	Cookie Response (play)		Pre
0x10 0x12	Serverbound Plugin Message (play)	Current	(unchanged)
0x13	Debug Sample Subscription		Pre
0x11 0x14	Edit Book	Current	(unchanged)
0x12 0x15	Query Entity Tag	Current	(unchanged)
0x13 0x16	Interact	Current	(unchanged)
0x14 0x17	Jigsaw Generate	Current	(unchanged)
0x15 0x18	Serverbound Keep Alive (play)	Current	(unchanged)
0x16 0x19	Lock Difficulty	Current	(unchanged)
0x17 0x1A	Set Player Position	Current	(unchanged)
0x18 0x1B	Set Player Position and Rotation	Current	(unchanged)
0x19 0x1C	Set Player Rotation	Current	(unchanged)
0x1A 0x1D	Set Player On Ground	Current	(unchanged)
0x1B 0x1E	Move Vehicle	Current	(unchanged)
0x1C 0x1F	Paddle Boat	Current	(unchanged)
0x1D 0x20	Pick Item	Current	(unchanged)
0x1E 0x21	Ping Request (play)	Current	(unchanged)
0x1F 0x22	Place Recipe	Current	(unchanged)
0x20 0x23	Player Abilities	Current	(unchanged)
0x21 0x24	Player Action	Current	(unchanged)
0x22 0x25	Player Command	Current	(unchanged)
0x23 0x26	Player Input	Current	(unchanged)
0x24 0x27	Pong (play)	Current	(unchanged)
0x25 0x28	Change Recipe Book Settings	Current	(unchanged)
0x26 0x29	Set Seen Recipe	Current	(unchanged)
0x27 0x2A	Rename Item	Current	(unchanged)
0x28 0x2B	Resource Pack Response (play)	Current	(unchanged)
0x29 0x2C	Seen Advancements	Current	(unchanged)
0x2A 0x2D	Select Trade	Current	(unchanged)
0x2B 0x2E	Set Beacon Effect	Current	(unchanged)
0x2C 0x2F	Set Held Item	Current	(unchanged)
0x2D 0x30	Program Command Block	Current	(unchanged)
0x2E 0x31	Program Command Block Minecart	Current	(unchanged)
0x2F 0x32	Set Creative Mode Slot	Current	(unchanged)
0x30 0x33	Program Jigsaw Block	Current	(unchanged)
0x31 0x34	Program Structure Block	Current	(unchanged)
0x32 0x35	Update Sign	Current	(unchanged)
0x33 0x36	Swing Arm	Current	(unchanged)
0x34 0x37	Teleport To Entity	Current	(unchanged)
0x35 0x38	Use Item On	Current	(unchanged)
0x36 0x39	Use Item	Current	(unchanged)

New/modified data types

No changes so far.

Entity Metadata

Type	Name	Value	Notes
0	Byte	Byte
1	VarInt	VarInt
2	VarLong	VarLong
3	Float	Float
4	String	String
5	Text Component	Text Component
6	Optional Text Component	(Boolean, Optional Text Component)	Text Component is present if the Boolean is set to true.
7	Slot	Slot
8	Boolean	Boolean
9	Rotations	(Float, Float, Float)	rotation on x, rotation on y, rotation on z
10	Position	Position
11	Optional Position	(Boolean, Optional Position)	Position is present if the Boolean is set to true.
12	Direction	VarInt Enum	Down = 0, Up = 1, North = 2, South = 3, West = 4, East = 5
13	Optional UUID	(Boolean, Optional UUID)	UUID is present if the Boolean is set to true.
14	Block State	VarInt	An ID in the block state registry.
15	Optional Block State	VarInt	0 for absent (air is unrepresentable); otherwise, an ID in the block state registry.
16	NBT	NBT
17	Particle	(VarInt, Varies)	particle type (an ID in the minecraft:particle_type registry), particle data (See Particles.)
18	Particles	(VarInt, Array of Particle)	length of array, particle data (See directly above.)
18 19	Villager Data	(VarInt, VarInt, VarInt)	villager type, villager profession, level (See below.)
19 20	Optional VarInt	VarInt	0 for absent; 1 + actual value otherwise. Used for entity IDs.
20 21	Pose	VarInt Enum	STANDING = 0, FALL_FLYING = 1, SLEEPING = 2, SWIMMING = 3, SPIN_ATTACK = 4, SNEAKING = 5, LONG_JUMPING = 6, DYING = 7, CROAKING = 8, USING_TONGUE = 9, SITTING = 10, ROARING = 11, SNIFFING = 12, EMERGING = 13, DIGGING = 14, SLIDING = 15, SHOOTING = 16, INHALING = 17
21 22	Cat Variant	VarInt	An ID in the minecraft:cat_variant registry.
22 23	Wolf Variant	VarInt	An ID in the minecraft:wolf_variant registry.
22 24	Frog Variant	VarInt	An ID in the minecraft:frog_variant registry.
23 25	Optional Global Position	(Boolean, Optional Identifier, Optional Position)	dimension identifier, position; only if the Boolean is set to true.
24 26	Painting Variant	VarInt	An ID in the minecraft:painting_variant registry.
25 27	Sniffer State	VarInt Enum	IDLING = 0, FEELING_HAPPY = 1, SCENTING = 2, SNIFFING = 3, SEARCHING = 4, DIGGING = 5, RISING = 6
26 28	Armadillo State	VarInt Enum	IDLE = 0, ROLLING = 1, SCARED = 2
26 29	Vector3	(Float, Float, Float)	x, y, z
27 30	Quaternion	(Float, Float, Float, Float)	x, y, z, w

Living Entity

TODO: This has changed to use the PARTICLES attribute

Wolf

Extends Tameable Animal.

Index	Type	Meaning		Default
0	Wolf Variant (22 23)	Wolf Variant		PALE
1	Boolean (8)	Is begging		false
2	VarInt (1)	Collar color (values are those used with dyes)		14 (Red)
3	VarInt (1)	Anger time		0

Armadillo

Extends Animal.

Index	Type	Meaning		Default
17	Armadillo State (26 28)	Armadillo State		IDLE

Block Actions

No changes so far.

Inventories

No changes so far.

Plugin Channels

No changes so far.

Handshake

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 765 in Minecraft 1.20.4).
			Server Address	String (255)	Hostname or IP, e.g. localhost or 127.0.0.1, that was used to connect. The Notchian server does not use this information. Note that SRV records are a simple redirect, e.g. if _minecraft._tcp.example.com points to mc.example.org, users connecting to example.com will provide example.org as server address in addition to connecting to it.
			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, 3 for Transfer.

Status

Clientbound

No changes so far.

Serverbound

No changes so far.

Login

Clientbound

Encryption Request

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x01	Login	Client	Server ID	String (20)	Appears to be empty.
			Public Key Length	VarInt	Length of Public Key.
			Public Key	Byte Array	The server's public key, in bytes.
			Verify Token Length	VarInt	Length of Verify Token. Always 4 for Notchian servers.
			Verify Token	Byte Array	A sequence of random bytes generated by the server.
			Should Authenticate	Boolean

Cookie Request (login)

Requests a cookie that was previously stored.

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x05	Login	Client	Key		Identifier		The identifier of the cookie.

Serverbound

Cookie Response (login)

Response to a Cookie Request (login) from the server. The Notchian server only accepts responses of up to 5 kiB in size.

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x04	Login	Server	Key		Identifier		The identifier of the cookie.
			Has Payload		Boolean		The payload is only present if the cookie exists on the client.
			Payload Length		VarInt		Length of the following byte array.
			Payload		Optional Byte Array (5120)		The data of the cookie, if any.

Configuration

Clientbound

Cookie Request (configuration)

Requests a cookie that was previously stored.

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x00	Configuration	Client	Key		Identifier		The identifier of the cookie.

Reset Chat

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x06	Configuration	Client	no fields

Registry Data

Represents certain registries that are sent from the server and are applied on the client. The packet is sent for each of the following registries: minecraft:worldgen/biome, minecraft:chat_type, minecraft:trim_pattern, minecraft:trim_material, minecraft:wolf_variant, minecraft:dimension_type, minecraft:damage_type, and minecraft:banner_pattern.

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x07	Configuration	Client	Registry Codec		NBT (Compound)		See Registry Data.
			Registry ID		Identifier
			Entry Count		VarInt		Number of entries in the following array.
			Entries	Entry ID	Array	Identifier
				Has Data		Boolean	Whether the entry has any data following.
				Data		NBT Tag	Entry data. Only present if Has Data is true.

Store Cookie (configuration)

Stores some arbitrary data on the client, which persists between server transfers. The Notchian client only accepts cookies of up to 5 kiB in size.

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x0A	Configuration	Client	Key		Identifier		The identifier of the cookie.
			Payload		ByteArray(5120)		The data of the cookie.

Transfer (configuration)

Notifies the client that it should transfer to the given server. Cookies previously stored are preserved between server transfers.

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x0B	Configuration	Client	Host		String		The hostname of IP of the server.
			Port		VarInt		The port of the server.

Clientbound Known Packs

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x0E	Configuration	Client	Known Pack Count		VarInt		The number of known packs in the following array.
			Known Packs	Namespace	Array	String
				ID		String
				Version		String

Serverbound

Cookie Response (configuration)

Response to a Cookie Request (configuration) from the server. The Notchian server only accepts responses of up to 5 kiB in size.

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x01	Configuration	Server	Key		Identifier		The identifier of the cookie.
			Has Payload		Boolean		The payload is only present if the cookie exists on the client.
			Payload Length		VarInt		Length of the following byte array.
			Payload		Optional Byte Array (5120)		The data of the cookie, if any.

Serverbound Known Packs

ID 0x07, same structure as Clientbound Known Packs. If the client specifies a pack in this packet, the server should omit its contained data from Registry Data.

Play

Clientbound

Cookie Request (play)

Requests a cookie that was previously stored.

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x16	Play	Client	Key		Identifier		The identifier of the cookie.

Debug Sample

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x1B	Play	Client	Sample Length	VarInt	The length of the following array.
			Sample	Long Array	TODO: What is the structure of the data in this array?
			Sample Type	VarInt Enum	The type of sample data. Currently always 0 (TICK_TIME).

Login (play)

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x2B	Play	Client	Entity ID	Int	The player's Entity ID (EID).
			Is hardcore	Boolean
			Dimension Count	VarInt	Size of the following array.
			Dimension Names	Array of Identifier	Identifiers for all dimensions on the server.
			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 VarInt	The ID of the type of dimension in the minecraft:dimension_type registry, defined by the Registry Data packet.
			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.
			Enforces Secure Chat	Boolean

Respawn

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x47	Play	Client	Dimension Type	Identifier VarInt	The ID of the type of dimension in the minecraft:dimension_type registry, defined by the Registry Data packet.
			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.
			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.

Store Cookie (play)

Stores some arbitrary data on the client, which persists between server transfers. The Notchian client only accepts cookies of up to 5 kiB in size.

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x6B	Play	Client	Key		Identifier		The identifier of the cookie.
			Payload Length		VarInt		Length of the following byte array.
			Payload		Byte Array (5120)		The data of the cookie.

Transfer (play)

Notifies the client that it should transfer to the given server. Cookies previously stored are preserved between server transfers.

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x73	Play	Client	Host		String		The hostname of IP of the server.
			Port		VarInt		The port of the server.

Update Attributes

Sets attributes on the given entity.

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x71	Play	Client	Entity ID		VarInt
			Number Of Properties		VarInt		Number of elements in the following array.
			Property	Key Id	Array	Identifier VarInt Enum	See below.
				Value		Double	See below.
				Number Of Modifiers		VarInt	Number of elements in the following array.
				Modifiers		Array of Modifier Data	See Attribute#Modifiers. Modifier Data defined below.

Known Key values (see also Attribute#Modifiers):

These changed between 24w03b and 24w13a, TODO: Update this

Id	Key	Default	Min	Max	Label
0	generic.armor	0.0	0.0	30.0	Armor.
1	generic.armor_toughness	0.0	0.0	20.0	Armor Toughness.
2	generic.attack_damage	2.0	0.0	2048.0	Attack Damage.
3	generic.attack_knockback	0.0	0.0	5.0	Attack Knockback.
4	generic.attack_speed	4.0	0.0	1024.0	Attack Speed.
5	generic.block_interaction_range	4.5	0.0	64.0	Block Interaction Range.
6	generic.entity_interaction_range	3.0	0.0	64.0	Entity Interaction Range.
7	generic.flying_speed	0.4	0.0	1024.0	Flying Speed.
8	generic.follow_range	32.0	0.0	2048.0	Follow Range.
9	horse.jump_strength	0.7	0.0	2.0	Jump Strength.
10	generic.knockback_resistance	0.0	0.0	1.0	Knockback Resistance.
11	generic.luck	0.0	-1024.0	1024.0	Luck.
12	generic.max_absorption	0.0	0.0	2048.0	Max Absorption.
13	generic.max_health	20.0	1.0	1024.0	Max Health.
14	generic.movement_speed	0.7	0.0	1024.0	Movement Speed.
15	generic.scale	1.0	0.0625	16.0	Scale.
16	zombie.spawn_reinforcements	0.0	0.0	1.0	Spawn Reinforcements Chance.
17	generic.step_height	0.6	0.0	10.0	Step Height.

Modifier Data structure:

Field Name	Field Type	Notes
UUID	UUID
Amount	Double	May be positive or negative.
Operation	Byte	See below.

The operation controls how the base value of the modifier is changed.

• 0: Add/subtract amount
• 1: Add/subtract amount percent of the current value
• 2: Multiply by amount percent

All of the 0's are applied first, and then the 1's, and then the 2's.

Entity Effect

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x72	Play	Client	Entity ID	VarInt
			Effect ID	VarInt	See this table.
			Amplifier	Byte	Notchian client displays effect level as Amplifier + 1.
			Duration	VarInt	Duration in ticks. (-1 for infinite)
			Flags	Byte	Bit field, see below.
			Has Factor Data	Boolean	Used in DARKNESS effect
			Factor Codec	NBT Tag	See below

	The following information needs to be added to this page:
	What exact effect does the blend bit flag have on the client? What happens if it is used on effects besides DARKNESS?

Within flags:

• 0x01: Is ambient - was the effect spawned from a beacon? All beacon-generated effects are ambient. Ambient effects use a different icon in the HUD (blue border rather than gray). If all effects on an entity are ambient, the "Is potion effect ambient" living metadata field should be set to true. Usually should not be enabled.
• 0x02: Show particles - should all particles from this effect be hidden? Effects with particles hidden are not included in the calculation of the effect color, and are not rendered on the HUD (but are still rendered within the inventory). Usually should be enabled.
• 0x04: Show icon - should the icon be displayed on the client? Usually should be enabled.
• 0x08: Blend - should the effect's hard-coded blending be applied? Currently only used in the DARKNESS effect to apply extra void fog and adjust the gamma value for lighting.

Factor Data

Name	Type	Notes
padding_duration	TAG_INT
factor_start	TAG_FLOAT
factor_target	TAG_FLOAT
factor_current	TAG_FLOAT
effect_changed_timestamp	TAG_INT
factor_previous_frame	TAG_FLOAT
had_effect_last_tick	TAG_BOOLEAN

Serverbound

Chat Command

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x04	Play	Server	Command		String (256)		The command typed by the client.
			Timestamp		Long		The timestamp that the command was executed.
			Salt		Long		The salt for the following argument signatures.
			Array length		VarInt		Number of entries in the following array. The maximum length in Notchian server is 8.
			Array of argument signatures	Argument name	Array (8)	String (16)	The name of the argument that is signed by the following signature.
				Signature		Byte Array (256)	The signature that verifies the argument. Always 256 bytes and is not length-prefixed.
			Message Count		VarInt
			Acknowledged		Fixed BitSet (20)

Signed Chat Command

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x05	Play	Server	Command		String(256)		The command typed by the client.
			Timestamp		Long		The timestamp that the command was executed. Milliseconds since the Unix epoch.
			Salt		Long		The salt for the following argument signatures.
			Argument Signature Count		VarInt		Number of elements in the following array. The maximum length in Notchian server is 8.
			Argument Signatures	Name	Array	String(16)	The name of the argument that is signed by the following signature.
				Signature		ByteArray(256)	The signature that verifies the argument. Always 256 bytes and is not length-prefixed.
			Seen Messages Offset		VarInt
			Seen Messages Acknowledged		Fixed BitSet(20)

Cookie Response (play)

Response to a Cookie Request (play) from the server. The Notchian server only accepts responses of up to 5 kiB in size.

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x11	Play	Server	Key		Identifier		The identifier of the cookie.
			Has Payload		Boolean		The payload is only present if the cookie exists on the client.
			Payload Length		Optional VarInt		Length of the following byte array.
			Payload		Optional Byte Array (5120)		The data of the cookie, if any.

Debug Sample Subscription

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x13	Play	Server	Sample Type	VarInt Enum	The type of debug sample to subscribe to. Currently always 0 (TICK_TIME).