Pre-release protocol

This page documents the changes from the last stable Minecraft release (currently 1.16.5, protocol 754) to the current pre-release (currently 1.17-rc2, protocol Snapshot 35). 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
Play clientbound
0x05	Sculk Vibration Signal		Pre
0x05 0x06	Entity Animation (clientbound)	Current	(unchanged)
0x06 0x07	Statistics	Current	(unchanged)
0x07 0x08	Acknowledge Player Digging	Current	(unchanged)
0x08 0x09	Block Break Animation	Current	(unchanged)
0x09 0x0A	Block Entity Data	Current	(unchanged)
0x0A 0x0B	Block Action	Current	(unchanged)
0x0B 0x0C	Block Change	Current	(unchanged)
0x0C 0x0D	Boss Bar	Current	(unchanged)
0x0D 0x0E	Server Difficulty	Current	(unchanged)
0x0E 0x0F	Chat Message (clientbound)	Current	(unchanged)
0x10	Clear Titles		Pre
0x0F 0x11	Tab-Complete (clientbound)	Current	(unchanged)
0x10 0x12	Declare Commands	Current	(unchanged)
0x11	Window Confirmation (clientbound)	Current
0x12 0x13	Close Window (clientbound)	Current	(unchanged)
0x13 0x14	Window Items	Current	(unchanged)
0x14 0x15	Window Property	Current	(unchanged)
0x15 0x16	Set Slot	Current	(unchanged)
0x16 0x17	Set Cooldown	Current	(unchanged)
0x17 0x18	Plugin Message (clientbound)	Current	(unchanged)
0x18 0x19	Named Sound Effect	Current	(unchanged)
0x19 0x1A	Disconnect (play)	Current	(unchanged)
0x1A 0x1B	Entity Status	Current	(unchanged)
0x1B 0x1C	Explosion	Current	Pre
0x1C 0x1D	Unload Chunk	Current	(unchanged)
0x1D 0x1E	Change Game State	Current	(unchanged)
0x1E 0x1F	Open Horse Window	Current	(unchanged)
0x20	Initialize World Border		Pre
0x1F 0x21	Keep Alive (clientbound)	Current	(unchanged)
0x20 0x22	Chunk Data	Current	Pre
0x21 0x23	Effect	Current	(unchanged)
0x22 0x24	Particle	Current	(unchanged)
0x23 0x25	Update Light	Current	Pre
0x24 0x26	Join Game	Current	Pre
0x25 0x27	Map Data	Current	Pre
0x26 0x28	Trade List	Current	(unchanged)
0x27 0x29	Entity Position	Current	(unchanged)
0x28 0x2A	Entity Position and Rotation	Current	(unchanged)
0x29 0x2B	Entity Rotation	Current	(unchanged)
0x2A	Entity Movement	Current
0x2B 0x2C	Vehicle Move (clientbound)	Current	(unchanged)
0x2C 0x2D	Open Book	Current	(unchanged)
0x2D 0x2E	Open Window	Current	(unchanged)
0x2E 0x2F	Open Sign Editor	Current	(unchanged)
0x30	Ping		Pre
0x2F 0x31	Craft Recipe Response	Current	(unchanged)
0x30 0x32	Player Abilities (clientbound)	Current	(unchanged)
0x31	Combat Event	Current
0x33	End Combat Event		Pre
0x34	Enter Combat Event		Pre
0x35	Death Combat Event		Pre
0x32 0x36	Player Info	Current	(unchanged)
0x33 0x37	Face Player	Current	(unchanged)
0x36	Destroy Entities	Current
0x34 0x38	Player Position And Look (clientbound)	Current	Pre
0x35 0x39	Unlock Recipes	Current	(unchanged)
0x3A	Destroy Entity		Pre
0x37 0x3B	Remove Entity Effect	Current	(unchanged)
0x38 0x3C	Resource Pack Send	Current	Pre
0x39 0x3D	Respawn	Current	(unchanged)
0x3A 0x3E	Entity Head Look	Current	(unchanged)
0x3B 0x3F	Multi Block Change	Current	(unchanged)
0x3C 0x40	Select Advancement Tab	Current	(unchanged)
0x41	Action Bar		Pre
0x42	World Border Center		Pre
0x43	World Border Lerp Size		Pre
0x44	World Border Size		Pre
0x45	World Border Warning Delay		Pre
0x46	World Border Warning Reach		Pre
0x3E 0x47	Camera	Current	(unchanged)
0x3F 0x48	Held Item Change (clientbound)	Current	(unchanged)
0x40 0x49	Update View Position	Current	(unchanged)
0x41 0x4A	Update View Distance	Current	(unchanged)
0x42 0x4B	Spawn Position	Current	Pre
0x43 0x4C	Display Scoreboard	Current	(unchanged)
0x44 0x4D	Entity Metadata	Current	(unchanged)
0x45 0x4E	Attach Entity	Current	(unchanged)
0x46 0x4F	Entity Velocity	Current	(unchanged)
0x47 0x50	Entity Equipment	Current	(unchanged)
0x4F	Title	Current
0x48 0x51	Set Experience	Current	(unchanged)
0x49 0x52	Update Health	Current	(unchanged)
0x4A 0x53	Scoreboard Objective	Current	(unchanged)
0x4B 0x54	Set Passengers	Current	(unchanged)
0x4C 0x55	Teams	Current	(unchanged)
0x4D 0x56	Update Score	Current	(unchanged)
0x57	Set Title SubTitle		Pre
0x4E 0x58	Time Update	Current	(unchanged)
0x59	Set Title Text		Pre
0x5A	Set Title Time		Pre
0x50 0x5B	Entity Sound Effect	Current	(unchanged)
0x51 0x5C	Sound Effect	Current	(unchanged)
0x52 0x5D	Stop Sound	Current	(unchanged)
0x53 0x5E	Player List Header And Footer	Current	(unchanged)
0x54 0x5F	NBT Query Response	Current	(unchanged)
0x55 0x60	Collect Item	Current	(unchanged)
0x56 0x61	Entity Teleport	Current	(unchanged)
0x57 0x62	Advancements	Current	(unchanged)
0x58 0x63	Entity Properties	Current	Pre
0x59 0x64	Entity Effect	Current	(unchanged)
0x5A 0x65	Declare Recipes	Current	(unchanged)
0x5B 0x66	Tags	Current	Pre
Play serverbound
0x05	Client Settings	Current	Pre
0x07	Window Confirmation (serverbound)	Current
0x08 0x07	Click Window Button	Current	(unchanged)
0x09 0x08	Click Window	Current	Pre
0x0A 0x09	Close Window (serverbound)	Current	(unchanged)
0x0B 0x0A	Plugin Message (serverbound)	Current	(unchanged)
0x0C 0x0B	Edit Book	Current	(unchanged)
0x0D 0x0C	Query Entity NBT	Current	(unchanged)
0x0E 0x0D	Interact Entity	Current	(unchanged)
0x0F 0x0E	Generate Structure	Current	(unchanged)
0x10 0x0F	Keep Alive (serverbound)	Current	(unchanged)
0x11 0x10	Lock Difficulty	Current	(unchanged)
0x12 0x11	Player Position	Current	(unchanged)
0x13 0x12	Player Position And Rotation (serverbound)	Current	(unchanged)
0x14 0x13	Player Rotation	Current	(unchanged)
0x15 0x14	Player Movement	Current	(unchanged)
0x16 0x15	Vehicle Move (serverbound)	Current	(unchanged)
0x17 0x16	Steer Boat	Current	(unchanged)
0x18 0x17	Pick Item	Current	(unchanged)
0x19 0x18	Craft Recipe Request	Current	(unchanged)
0x1A 0x19	Player Abilities (serverbound)	Current	(unchanged)
0x1B 0x1A	Player Digging	Current	(unchanged)
0x1C 0x1B	Entity Action	Current	(unchanged)
0x1D 0x1C	Steer Vehicle	Current	(unchanged)
0x1D	Pong		Pre
Handshaking serverbound
0x00	Handshake	Current	Pre

New/modified data types

No changes so far.

Entity Metadata

Note that other entities have had metadata shifts due to these changes, not shown here.

Entity

The base class.

Index	Type	Meaning		Default
0	Byte	Bit mask	Meaning	0
		0x01	Is on fire
		0x02	Is crouching
		0x04	Unused (previously riding)
		0x08	Is sprinting
		0x10	Is swimming
		0x20	Is invisible
		0x40	has glowing effect
		0x80	Is flying with an elytra
1	VarInt	Air ticks		300
2	OptChat	Custom name		empty
3	Boolean	Is custom name visible		false
4	Boolean	Is silent		false
5	Boolean	Has no gravity		false
6	Pose	Pose		STANDING
7	VarInt	Ticks frozen in powdered snow		0

Block Actions

No changes so far.

Inventories

No changes so far.

Plugin Channels

No changes so far.

Play

Clientbound

Sculk Vibration Signal

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x05	Play	Client	Source Position	Position	Source position for the vibration.
			Destination Identifier	Identifier	Identifier of the destination codec type.
			Destination	Varies	Vanilla default destinations are a block position encoded as a Position for "block" or an entity id encoded as a VarInt for "entity".
			Arrival Ticks	VarInt	Ticks for the signal to arrive at the destination.

This packet shows a permanent particle.

Clear Titles

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x10	Play	Client
			Reset	Boolean

Explosion

Sent when an explosion occurs (creepers, TNT, and ghast fireballs).

Each block in Records is set to air. Coordinates for each axis in record is int(X) + record.x

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x1B 0x1C	Play	Client	X	Float
			Y	Float
			Z	Float
			Strength	Float	A strength greater than or equal to 2.0 spawns a minecraft:explosion_emitter particle, while a lesser strength spawns a minecraft:explosion particle.
			Record Count	Int VarInt	Number of elements in the following array.
			Records	Array of (Byte, Byte, Byte)	Each record is 3 signed bytes long; the 3 bytes are the XYZ (respectively) signed offsets of affected blocks.
			Player Motion X	Float	X velocity of the player being pushed by the explosion.
			Player Motion Y	Float	Y velocity of the player being pushed by the explosion.
			Player Motion Z	Float	Z velocity of the player being pushed by the explosion.

Initialize World Border

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x20	Play	Client	X	Double
			Z	Double
			Old Diameter	Double	Current length of a single side of the world border, in meters.
			New Diameter	Double	Target length of a single side of the world border, in meters.
			Speed	VarLong	Number of real-time milliseconds until New Diameter is reached. It appears that Notchian server does not sync world border speed to game ticks, so it gets out of sync with server lag. If the world border is not moving, this is set to 0.
			Portal Teleport Boundary	VarInt	Resulting coordinates from a portal teleport are limited to ±value. Usually 29999984.
			Warning Blocks	VarInt	In meters.
			Warning Time	VarInt	In seconds as set by /worldborder warning time.

The Notchian client determines how solid to display the warning by comparing to whichever is higher, the warning distance or whichever is lower, the distance from the current diameter to the target diameter or the place the border will be after warningTime seconds. In pseudocode:

distance = max(min(resizeSpeed * 1000 * warningTime, abs(targetDiameter - currentDiameter)), warningDistance);
if (playerDistance < distance) {
    warning = 1.0 - playerDistance / distance;
} else {
    warning = 0.0;
}

Chunk Data

Main article: Chunk Format

See also: #Unload Chunk

	The following information needs to be added to this page:
	How do biomes work now? The biome change happened at the same time as the seed change, but it's not clear how/if biomes could be computed given that it's not the actual seed... (/r/mojira discussion which notes that it seems to be some kind of interpolation, and 3D biomes are only used in the nether)

The server only sends skylight information for chunk pillars in the Overworld, it's up to the client to know in which dimension 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 0x22	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)
			Full chunk	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).
			Bit Mask Length	VarInt	Length of the following array
			Primary Bit Mask	Array of Long	BitSet with bits (world height in blocks / 16) 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 the lowest y to 15 blocks above).
			Heightmaps	NBT	Compound containing one long array named MOTION_BLOCKING, which is a heightmap for the highest solid block at each position in the chunk (as a compacted long array with 256 entries at 9 bits per entry totaling 36 longs). The Notchian server also adds a WORLD_SURFACE long array, the purpose of which is unknown, but it's not required for the chunk to be accepted.
			Biomes length	Optional VarInt	Size of the following array; should always be 1024. Not present if full chunk is false.
			Biomes	Optional Array of VarInt	1024 biome IDs, ordered by x then z then y, in 4×4×4 blocks. Not present if full chunk is false. See Chunk Format § Biomes.
			Size	VarInt	Size of Data in bytes
			Data	Byte array	See data structure in Chunk Format
			Number of block entities	VarInt	Number of elements in 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.

Note that the Notchian client requires an Update View Position packet when it crosses a chunk border, otherwise it'll only display render distance + 2 chunks around the chunk it spawned in.

The compacted array format has been adjusted so that individual entries no longer span across multiple longs, affecting the main data array and heightmaps.

New format, 5 bits per block, containing the following references to blocks in a palette (not shown): 122344566480743131516914101202

0020863148418841 0000000000100000100001100011000101001000010000011000100001000001
01018A7260F68C87 0000000100000001100010100111001001100000111101101000110010000111

Entity Movement

This packet may be used to initialize an entity.

For player entities, either this packet or any move/look packet is sent every game tick. So the meaning of this packet is basically that the entity did not move/look since the last such packet.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x2A	Play	Client	Entity ID	VarInt

Ping

Unknown what this packet does just yet, not used by the Notchian server or client.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x30	Play	Client	ID	Int

Update Light

Updates light levels for a chunk.

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x23 0x25	Play	Client	Chunk X		VarInt		Chunk coordinate (block coordinate divided by 16, rounded down)
			Chunk Z		VarInt		Chunk coordinate (block coordinate divided by 16, rounded down)
			Trust Edges		Boolean		If edges should be trusted for light updates.
			Sky Light Mask		VarInt		Mask containing 18 bits, with the lowest bit corresponding to chunk section -1 (in the void, y=-16 to y=-1) and the highest bit for chunk section 16 (above the world, y=256 to y=271)
			Block Light Mask		VarInt		Mask containing 18 bits, with the same order as sky light
			Empty Sky Light Mask		VarInt		Mask containing 18 bits, which indicates sections that have 0 for all their sky light values. If a section is set in both this mask and the main sky light mask, it is ignored for this mask and it is included in the sky light arrays (the notchian server does not create such masks). If it is only set in this mask, it is not included in the sky light arrays.
			Empty Block Light Mask		VarInt		Mask containing 18 bits, which indicates sections that have 0 for all their block light values. If a section is set in both this mask and the main block light mask, it is ignored for this mask and it is included in the block light arrays (the notchian server does not create such masks). If it is only set in this mask, it is not included in the block light arrays.
			Length 1		VarInt		Length of the following array
			Sky Light Mask		Array of Long		BitSet containing bits for each sections in the world + 2 (lowest bit 16-1 blocks below min world height, highest 1-16 above max world height)
			Length 2		VarInt		Length of the following array
			Block Light Mask		Array of Long		BitSet containing bits for each sections in the world + 2, same order as sky light
			Length 3		VarInt		Length of the following array
			Empty Sky Light Mask		Array of Long		BitSet containing a variable amount of bits (see sky/block light) which indicates sections that have 0 for all their sky light values
			Length 4		VarInt		Length of the following array
			Empty Block Light Mask		Array of Long		BitSet containing a variable amount of bits (see sky/block light) which indicates sections that have 0 for all their block light values
			Sky Light array count		VarInt		Number of entries in the following array
			Sky Light arrays	Length	Array	VarInt	Length of the following array in bytes (always 2048)
				Sky Light array		Array of 2048 bytes	There is 1 array for each bit set to true in the sky light mask, starting with the lowest value. Half a byte per light value.
			Block Light array count		VarInt		Number of entries in the following array
			Block Light arrays	Length	Array	VarInt	Length of the following array in bytes (always 2048)
				Block Light array		Array of 2048 bytes	There is 1 array for each bit set to true in the block light mask, starting with the lowest value. Half a byte per light value.

Join Game

See Protocol Encryption for information on logging in.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x24 0x26	Play	Client	Entity ID	Int	The player's Entity ID (EID).
			Is hardcore	Boolean
			Gamemode	Unsigned Byte	0: Survival, 1: Creative, 2: Adventure, 3: Spectator.
			Previous Gamemode	Byte	0: survival, 1: creative, 2: adventure, 3: spectator. The hardcore flag is not included. The previous gamemode. Defaults to -1 if there is no previous gamemode. (More information needed)
			World Count	VarInt	Size of the following array.
			World Names	Array of Identifier	Identifiers for all worlds on the server.
			Dimension Codec	NBT Tag Compound	The full extent of these is still unknown, but the tag represents a dimension and biome registry. See below for the vanilla default.
			Dimension	NBT Tag Compound	Valid dimensions are defined per dimension registry sent before this. The structure of this tag is a dimension type (see below).
			World Name	Identifier	Name of the world 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).
			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.
			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.

The Dimension Codec NBT Tag Compound (Default value in SNBT) includes two registries: "minecraft:dimension_type" and "minecraft:worldgen/biome".

Name	Type	Notes
minecraft:dimension_type	TAG_Compound	The dimension type registry (see below).
minecraft:worldgen/biome	TAG_Compound	The biome 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.
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.
has_raids	TAG_Byte	Whether players with the Bad Omen effect can cause a raid.		1: true, 0: false.
min_y	TAG_Int	The minimum Y level.
height	TAG_Int	The maximum height.
logical_height	TAG_Int	The maximum height to which chorus fruits and nether portals can bring players within this dimension.		0-256.
coordinate_scale	TAG_Float	The multiplier applied to coordinates when traveling to the dimension.		1: true, 0: false.
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
precipitation		TAG_String		The type of precipitation in the biome.		"rain", "snow", or "none".
depth		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		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		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	Optional TAG_Compound	Particles that appear randomly in the biome.		If present, contains the fields: probability (TAG_Float), options (TAG_Compound). The "options" compound contains the field "type" (TAG_String), which identifies the particle type.

Map Data

Updates a rectangular area on a map item.

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x25 0x27	Play	Client	Map ID		VarInt		Map ID of the map being modified
			Scale		Byte		From 0 for a fully zoomed-in map (1 block per pixel) to 4 for a fully zoomed-out map (16 blocks per pixel)
			Tracking Position		Boolean		Specifies whether player and item frame icons are shown
			Locked		Boolean		True if the map has been locked in a cartography table
			Tracking Position		Boolean		Specifies whether player and item frame icons are shown
			Icon Count		VarInt		Number of elements in the following array. Only present if "Tracking Position" is true.
			Icon	Type	Array	VarInt enum	See below
				X		Byte	Map coordinates: -128 for furthest left, +127 for furthest right
				Z		Byte	Map coordinates: -128 for highest, +127 for lowest
				Direction		Byte	0-15
				Has Display Name		Boolean
				Display Name		Optional Chat	Only present if previous Boolean is true
			Columns		Unsigned Byte		Number of columns updated
			Rows		Optional Byte		Only if Columns is more than 0; number of rows updated
			X		Optional Byte		Only if Columns is more than 0; x offset of the westernmost column
			Z		Optional Byte		Only if Columns is more than 0; z offset of the northernmost row
			Length		Optional VarInt		Only if Columns is more than 0; length of the following array
			Data		Optional Array of Unsigned Byte		Only if Columns is more than 0; see Map item format

For icons, a direction of 0 is a vertical icon and increments by 22.5° (360/16).

Types are based off of rows and columns in map_icons.png:

Icon type	Result
0	White arrow (players)
1	Green arrow (item frames)
2	Red arrow
3	Blue arrow
4	White cross
5	Red pointer
6	White circle (off-map players)
7	Small white circle (far-off-map players)
8	Mansion
9	Temple
10	White Banner
11	Orange Banner
12	Magenta Banner
13	Light Blue Banner
14	Yellow Banner
15	Lime Banner
16	Pink Banner
17	Gray Banner
18	Light Gray Banner
19	Cyan Banner
20	Purple Banner
21	Blue Banner
22	Brown Banner
23	Green Banner
24	Red Banner
25	Black Banner
26	Treasure marker

Combat Event

Originally used for metadata for twitch streaming circa 1.8. Now only used to display the game over screen (with enter combat and end combat completely ignored by the Notchain client)

Packet ID	State	Bound To	Field Name		Field Type	Notes
0x31	Play	Client	Event		VarInt Enum	Determines the layout of the remaining packet.
			Event	Field Name
			0: enter combat	no fields	no fields
			1: end combat	Duration	VarInt	Length of the combat in ticks.
				Entity ID	Int	ID of the primary opponent of the ended combat, or -1 if there is no obvious primary opponent.
			2: entity dead	Player ID	VarInt	Entity ID of the player that died (should match the client's entity ID).
				Entity ID	Int	The killing entity's ID, or -1 if there is no obvious killer.
				Message	Chat	The death message.

End Combat Event

Unused by the Notchain client.

Packet ID	State	Bound To	Field Name		Field Type	Notes
0x33	Play	Client	Duration	VarInt	Length of the combat in ticks.
			Entity ID	Int	ID of the primary opponent of the ended combat, or -1 if there is no obvious primary opponent.

Enter Combat Event

Unused by the Notchain client.

Packet ID	State	Bound To	Field Name		Field Type	Notes
0x34	Play	Client

Death Combat Event

Used to send a respawn screen.

Packet ID	State	Bound To	Field Name		Field Type	Notes
0x35	Play	Client	Player ID	VarInt	Entity ID of the player that died (should match the client's entity ID).
			Entity ID	Int	The killing entity's ID, or -1 if there is no obvious killer.
			Message	Chat	The death message.

Player Position And Look (clientbound)

Updates the player's position on the server. This packet will also close the “Downloading Terrain” screen when joining/respawning.

If the distance between the last known position of the player on the server and the new position set by this packet is greater than 100 meters, the client will be kicked for “You moved too quickly :( (Hacking?)”.

Also if the fixed-point number of X or Z is set greater than 3.2E7D the client will be kicked for “Illegal position”.

Yaw is measured in degrees, and does not follow classical trigonometry rules. The unit circle of yaw on the XZ-plane starts at (0, 1) and turns counterclockwise, with 90 at (-1, 0), 180 at (0, -1) and 270 at (1, 0). Additionally, yaw is not clamped to between 0 and 360 degrees; any number is valid, including negative numbers and numbers greater than 360.

Pitch is measured in degrees, where 0 is looking straight ahead, -90 is looking straight up, and 90 is looking straight down.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x34 0x38	Play	Client	X	Double	Absolute or relative position, depending on Flags.
			Y	Double	Absolute or relative position, depending on Flags.
			Z	Double	Absolute or relative position, depending on Flags.
			Yaw	Float	Absolute or relative rotation on the X axis, in degrees.
			Pitch	Float	Absolute or relative rotation on the Y axis, in degrees.
			Flags	Byte	Bit field, see below.
			Teleport ID	VarInt	Client should confirm this packet with Teleport Confirm containing the same Teleport ID.
			Dismount Vehicle	Boolean	True if the player should dismount their vehicle.

About the Flags field:

<Dinnerbone> It's a bitfield, X/Y/Z/Y_ROT/X_ROT. If X is set, the x value is relative and not absolute.

Field	Bit
X	0x01
Y	0x02
Z	0x04
Y_ROT	0x08
X_ROT	0x10

Destroy Entity

Sent by the server when a list of entities an entity is to be destroyed on the client.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x3A	Play	Client
			Count	VarInt	Number of elements in the following array.
			Array of VarInt	The list of entities of destroy.
			Entity ID	VarInt

Resource Pack Send

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x38 0x3C	Play	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. (must be lower case in order to work) 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.
			Forced Message	Chat	This is sent with the force resourcepack popup.

Title

Packet ID	State	Bound To	Field Name		Field Type	Notes
0x4F	Play	Client	Action		VarInt Enum
			Action	Field Name
			0: set title	Title Text	Chat
			1: set subtitle	Subtitle Text	Chat
			2: set action bar	Action bar text	Chat	Displays a message above the hotbar (the same as position 2 in Chat Message (clientbound).
			3: set times and display	Fade In	Int	Ticks to spend fading in.
				Stay	Int	Ticks to keep the title displayed.
				Fade Out	Int	Ticks to spend out, not when to start fading out.
			4: hide	no fields	no fields
			5: reset	no fields	no fields

“Hide” makes the title disappear, but if you run times again the same title will appear. “Reset” erases the text.

The title is visible on screen for Fade In + Stay + Fade Out ticks.

Action Bar

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x41	Play	Client	Action bar text	Chat	Displays a message above the hotbar (the same as position 2 in Chat Message (clientbound).

World Border Center

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x42	Play	Client	X	Double
			Z	Double

World Border Lerp Size

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x43	Play	Client	Old Diameter	Double	Current length of a single side of the world border, in meters.
			New Diameter	Double	Target length of a single side of the world border, in meters.
			Speed	VarLong	Number of real-time milliseconds until New Diameter is reached. It appears that Notchian server does not sync world border speed to game ticks, so it gets out of sync with server lag. If the world border is not moving, this is set to 0.

World Border Size

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x44	Play	Client	Diameter	Double	Length of a single side of the world border, in meters.

World Border Warning Delay

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x45	Play	Client	Warning Time	VarInt	In seconds as set by /worldborder warning time.

World Border Warning Reach

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x46	Play	Client	Warning Blocks	VarInt	In meters.

Spawn Position

Sent by the server after login to specify the coordinates of the spawn point (the point at which players spawn at, and which the compass points to). It can be sent at any time to update the point compasses point at.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x42 0x4B	Play	Client	Location	Position	Spawn location.
			Angle	Float

Set Title SubTitle

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x57	Play	Client	Subtitle Text	Chat

Set Title Text

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x59	Play	Client	Title Text	Chat

Set Title Time

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x5A	Play	Client	Fade In	Int	Ticks to spend fading in.
			Stay	Int	Ticks to keep the title displayed.
			Fade Out	Int	Ticks to spend out, not when to start fading out.

Entity Properties

Sets attributes on the given entity.

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x58 0x63	Play	Client	Entity ID		VarInt
			Number Of Properties		Int VarInt		Number of elements in the following array.
			Property	Key	Array	Identifier	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):

Key	Default	Min	Max	Label
generic.max_health	20.0	0.0	1024.0	Max Health.
generic.follow_range	32.0	0.0	2048.0	Follow Range.
generic.knockback_resistance	0.0	0.0	1.0	Knockback Resistance.
generic.movement_speed	0.7	0.0	1024.0	Movement Speed.
generic.attack_damage	2.0	0.0	2048.0	Attack Damage.
generic.attack_speed	4.0	0.0	1024.0	Attack Speed.
generic.flying_speed	0.4	0.0	1024.0	Flying Speed.
generic.armor	0.0	0.0	30.0	Armor.
generic.armor_toughness	0.0	0.0	20.0	Armor Toughness.
generic.attack_knockback	0.0	0.0	5.0	—
generic.luck	0.0	-1024.0	1024.0	Luck.
horse.jump_strength	0.7	0.0	2.0	Jump Strength.
zombie.spawn_reinforcements	0.0	0.0	1.0	Spawn Reinforcements Chance.
generic.reachDistance	5.0	0.0	1024.0	Player Reach Distance (Forge only).
forge.swimSpeed	1.0	0.0	1024.0	Swimming Speed (Forge only).

Unknown attributes will cause a game crash (MC-150405) due to the default minimum being larger than the default value.

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.

Tags

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x5B 0x66	Play	Client
			Block Tags		(See below)		IDs are block IDs
			Item Tags		(See below)		IDs are item IDs
			Fluid Tags		(See below)		IDs are fluid IDs
			Entity Tags		(See below)		IDs are entity IDs
			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.).

Serverbound

Client Settings

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

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x05	Play	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.
			Displayed Skin Parts	Unsigned Byte	Bit mask, see below.
			Main Hand	VarInt Enum	0: Left, 1: Right.
			Disable text filtering	Boolean	Disables filtering of text on signs and written book titles. Currently always true (i.e. the filtering is disabled)

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.

Window Confirmation (serverbound)

If a confirmation sent by the client was not accepted, the server will reply with a Window Confirmation (clientbound) packet with the Accepted field set to false. When this happens, the client must send this packet to apologize (as with movement), otherwise the server ignores any successive confirmations.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x07	Play	Server	Window ID	Byte	The ID of the window that the action occurred in.
			Action Number	Short	Every action that is to be accepted has a unique number. This number is an incrementing integer (starting at 1) with separate counts for each window ID.
			Accepted	Boolean	Whether the action was accepted.

Click Window

This packet is sent by the client when the player clicks on a slot in a window.

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x09 0x08	Play	Server	Window ID		Unsigned Byte		The ID of the window which was clicked. 0 for player inventory.
			Slot		Short		The clicked slot number, see below.
			Button		Byte		The button used in the click, see below.
			Action Number		Short		A unique number for the action, implemented by Notchian as a counter, starting at 1 (different counter for every window ID). Used by the server to send back a Window Confirmation (clientbound).
			Mode		VarInt Enum		Inventory operation mode, see below.
			Length of the array		VarInt
			Array of slots	Slot number	Array	Short
				Slot data		Slot	New data for this slot
			Clicked item		Slot		The clicked slot. Has to be empty (item ID = -1) for drop mode. Is always empty for mode 2 and mode 5 packets.

See Inventory for further information about how slots are indexed.

When right-clicking on a stack of items, half the stack will be picked up and half left in the slot. If the stack is an odd number, the half left in the slot will be smaller of the amounts.

The distinct type of click performed by the client is determined by the combination of the Mode and Button fields.

Mode	Button	Slot	Trigger
0	0	Normal	Left mouse click
	1	Normal	Right mouse click
	0	-999	Left click outside inventory (drop cursor stack)
	1	-999	Right click outside inventory (drop cursor single item)
1	0	Normal	Shift + left mouse click
	1	Normal	Shift + right mouse click (identical behavior)
2	0	Normal	Number key 1
	1	Normal	Number key 2
	2	Normal	Number key 3
	⋮	⋮	⋮
	8	Normal	Number key 9
3	2	Normal	Middle click, only defined for creative players in non-player inventories.
4	0	Normal*	Drop key (Q) (* Clicked item is always empty)
5	0	-999	Starting left mouse drag
	4	-999	Starting right mouse drag
	8	-999	Starting middle mouse drag, only defined for creative players in non-player inventories. (Note: the vanilla client will still incorrectly send this for non-creative players - see MC-46584)
	1	Normal	Add slot for left-mouse drag
	5	Normal	Add slot for right-mouse drag
	9	Normal	Add slot for middle-mouse drag, only defined for creative players in non-player inventories. (Note: the vanilla client will still incorrectly send this for non-creative players - see MC-46584)
	2	-999	Ending left mouse drag
	6	-999	Ending right mouse drag
	10	-999	Ending middle mouse drag, only defined for creative players in non-player inventories. (Note: the vanilla client will still incorrectly send this for non-creative players - see MC-46584)
6	0	Normal	Double click

Starting from version 1.5, “painting mode” is available for use in inventory windows. It is done by picking up stack of something (more than 1 item), then holding mouse button (left, right or middle) and dragging held stack over empty (or same type in case of right button) slots. In that case client sends the following to server after mouse button release (omitting first pickup packet which is sent as usual):

1. packet with mode 5, slot -999, button (0 for left | 4 for right);
2. packet for every slot painted on, mode is still 5, button (1 | 5);
3. packet with mode 5, slot -999, button (2 | 6);

If any of the painting packets other than the “progress” ones are sent out of order (for example, a start, some slots, then another start; or a left-click in the middle) the painting status will be reset.

The server will send back a Window Confirmation packet. If the click was not accepted, the client must send a matching serverbound window confirmation packet before sending more Click Window packets, otherwise the server will reject them silently. The Notchian server also sends a Window Items packet for the open window and Set Slot packets for the clicked and cursor slot, but only when the click was not accepted, probably to resynchronize client and server.

Pong

A response to the ping packet. Unknown what this is used for, this is ignored by the Notchian client and server.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x1D	Play	Server	ID	Int

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 754 Snapshot 15)
			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. Note that SRV records are a complete simple redirect, e.g. if _minecraft._tcp.example.com points to mc.example.org, users connecting to example.com will provide mc.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

Status

Clientbound

No changes so far.

Serverbound

No changes so far.

Login

Clientbound

No changes so far.

Serverbound

No changes so far.