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 21w05a, protocol Snapshot 12). 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)
0x0F 0x10	Tab-Complete (clientbound)	Current	(unchanged)
0x10 0x11	Declare Commands	Current	(unchanged)
0x11 0x12	Window Confirmation (clientbound)	Current	(unchanged)
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	(unchanged)
0x1C 0x1D	Unload Chunk	Current	(unchanged)
0x1D 0x1E	Change Game State	Current	(unchanged)
0x1E 0x1F	Open Horse Window	Current	(unchanged)
0x1F 0x20	Keep Alive (clientbound)	Current	(unchanged)
0x20 0x21	Chunk Data	Current	Pre
0x21 0x22	Effect	Current	(unchanged)
0x22 0x23	Particle	Current	(unchanged)
0x23 0x24	Update Light	Current	Pre
0x24 0x25	Join Game	Current	(unchanged)
0x25 0x26	Map Data	Current	Pre
0x26 0x27	Trade List	Current	(unchanged)
0x27 0x28	Entity Position	Current	(unchanged)
0x28 0x29	Entity Position and Rotation	Current	(unchanged)
0x29 0x2A	Entity Rotation	Current	(unchanged)
0x2A 0x2B	Entity Movement	Current	(unchanged)
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)
0x2F 0x30	Craft Recipe Response	Current	(unchanged)
0x30 0x31	Player Abilities (clientbound)	Current	(unchanged)
0x31 0x32	Combat Event	Current	(unchanged)
0x32 0x33	Player Info	Current	(unchanged)
0x33 0x34	Face Player	Current	(unchanged)
0x34 0x35	Player Position And Look (clientbound)	Current	Pre
0x35 0x36	Unlock Recipes	Current	(unchanged)
0x36 0x37	Destroy Entities	Current	(unchanged)
0x37 0x38	Remove Entity Effect	Current	(unchanged)
0x38 0x39	Resource Pack Send	Current	Pre
0x39 0x3A	Respawn	Current	(unchanged)
0x3A 0x3B	Entity Head Look	Current	(unchanged)
0x3B 0x3C	Multi Block Change	Current	(unchanged)
0x3C 0x3D	Select Advancement Tab	Current	(unchanged)
0x3D 0x3E	World Border	Current	(unchanged)
0x3E 0x3F	Camera	Current	(unchanged)
0x3F 0x40	Held Item Change (clientbound)	Current	(unchanged)
0x40 0x41	Update View Position	Current	(unchanged)
0x41 0x42	Update View Distance	Current	(unchanged)
0x42 0x43	Spawn Position	Current	(unchanged)
0x43 0x44	Display Scoreboard	Current	(unchanged)
0x44 0x45	Entity Metadata	Current	(unchanged)
0x45 0x46	Attach Entity	Current	(unchanged)
0x46 0x47	Entity Velocity	Current	(unchanged)
0x47 0x48	Entity Equipment	Current	(unchanged)
0x48 0x49	Set Experience	Current	(unchanged)
0x49 0x4A	Update Health	Current	(unchanged)
0x4A 0x4B	Scoreboard Objective	Current	(unchanged)
0x4B 0x4C	Set Passengers	Current	(unchanged)
0x4C 0x4D	Teams	Current	(unchanged)
0x4D 0x4E	Update Score	Current	(unchanged)
0x4E 0x4F	Time Update	Current	(unchanged)
0x4F 0x50	Title	Current	(unchanged)
0x50 0x51	Entity Sound Effect	Current	(unchanged)
0x51 0x52	Sound Effect	Current	(unchanged)
0x52 0x53	Stop Sound	Current	(unchanged)
0x53 0x54	Player List Header And Footer	Current	(unchanged)
0x54 0x55	NBT Query Response	Current	(unchanged)
0x55 0x56	Collect Item	Current	(unchanged)
0x56 0x57	Entity Teleport	Current	(unchanged)
0x57 0x58	Advancements	Current	(unchanged)
0x58 0x59	Entity Properties	Current	(unchanged)
0x59 0x5A	Entity Effect	Current	(unchanged)
0x5A 0x5B	Declare Recipes	Current	(unchanged)
0x5B 0x5C	Tags	Current	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 long 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

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 0x21	Play	Client	Chunk X	Int	Chunk coordinate (block coordinate divided by 16, rounded down)
			Chunk Z	Int	Chunk coordinate (block coordinate divided by 16, rounded down)
			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	VarInt	Size of the following array. Not present if full chunk is false.
			Biomes	Array of VarInt	1024 biome IDs, ordered by x then z then y, in 4×4×4 blocks. Possibly something else. Not present if full chunk is false.
			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

Update Light

Updates light levels for a chunk.

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x23 0x24	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.

Map Data

Updates a rectangular area on a map item.

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x25 0x26	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

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 0x35	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.
			Unknown	Boolean

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

Resource Pack Send

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x38 0x39	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.

Tags

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x5B 0x5C	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

No changes so far.

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 12)
			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 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.