Pre-release protocol

This page documents the changes from the last stable Minecraft release (currently 1.14.4, protocol 498) to the current pre-release (currently 19w40a, protocol 557). Note that this page contains bleeding-edge information that may not be completely or correctly documented.

One who wishes to commandeer the merging of this into Protocol when an update is made must be sure to respect any changes that may have occurred to the respective packets there.

Contents

Data types

No changes so far.

Packets

ID	Packet name	Documentation
Handshaking serverbound
0x00	Handshake	Current	Pre
Play clientbound
0x03	Spawn Mob	Current	Pre
0x05	Spawn Player	Current	Pre
0x5C 0x08	Player Digging	Current	(unchanged)
0x08 0x09	Block Break Animation	Current	(unchanged)
0x09 0x0A	Update Block Entity	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	Multi Block Change	Current	(unchanged)
0x10 0x11	Tab-Complete (clientbound)	Current	(unchanged)
0x11 0x12	Declare Commands	Current	(unchanged)
0x12 0x13	Confirm Transaction (clientbound)	Current	(unchanged)
0x13 0x14	Close Window (clientbound)	Current	(unchanged)
0x14 0x15	Window Items	Current	(unchanged)
0x15 0x16	Window Property	Current	(unchanged)
0x16 0x17	Set Slot	Current	(unchanged)
0x17 0x18	Set Cooldown	Current	(unchanged)
0x18 0x19	Plugin Message (clientbound)	Current	(unchanged)
0x19 0x1A	Named Sound Effect	Current	(unchanged)
0x1A 0x1B	Disconnect (play)	Current	(unchanged)
0x1B 0x1C	Entity Status	Current	(unchanged)
0x1C 0x1D	Explosion	Current	(unchanged)
0x1D 0x1E	Unload Chunk	Current	(unchanged)
0x1E 0x1F	Change Game State	Current	(unchanged)
0x1F 0x20	Open Horse Window	Current	(unchanged)
0x20 0x21	Keep Alive (clientbound)	Current	(unchanged)
0x21 0x22	Chunk Data	Current	Pre
0x22 0x23	Effect	Current	(unchanged)
0x23 0x24	Particle	Current	(unchanged)
0x24 0x25	Update Light	Current	(unchanged)
0x25 0x26	Join Game	Current	Pre
0x26 0x27	Map Data	Current	(unchanged)
0x27 0x28	Trade List	Current	(unchanged)
0x28 0x29	Entity Relative Move	Current	(unchanged)
0x29 0x2A	Entity Look And Relative Move	Current	(unchanged)
0x2A 0x2B	Entity Look	Current	(unchanged)
0x2B 0x2C	Entity	Current	(unchanged)
0x2C 0x2D	Vehicle Move (clientbound)	Current	(unchanged)
0x2D 0x2E	Open Book	Current	(unchanged)
0x2E 0x2F	Open Window	Current	(unchanged)
0x2F 0x30	Open Sign Editor	Current	(unchanged)
0x30 0x31	Craft Recipe Response	Current	(unchanged)
0x31 0x32	Player Abilities (clientbound)	Current	(unchanged)
0x32 0x33	Combat Event	Current	(unchanged)
0x33 0x34	Player Info	Current	(unchanged)
0x34 0x35	Face Player	Current	(unchanged)
0x35 0x36	Player Position And Look (clientbound)	Current	(unchanged)
0x36 0x37	Unlock Recipes	Current	(unchanged)
0x37 0x38	Destroy Entities	Current	(unchanged)
0x38 0x39	Remove Entity Effect	Current	(unchanged)
0x39 0x3A	Resource Pack Send	Current	(unchanged)
0x3A 0x3B	Respawn	Current	Pre
0x3B 0x3C	Entity Head Look	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	Display Scoreboard	Current	(unchanged)
0x43 0x44	Entity Metadata	Current	(unchanged)
0x44 0x45	Attach Entity	Current	(unchanged)
0x45 0x46	Entity Velocity	Current	(unchanged)
0x46 0x47	Entity Equipment	Current	(unchanged)
0x47 0x48	Set Experience	Current	(unchanged)
0x48 0x49	Update Health	Current	(unchanged)
0x49 0x4A	Scoreboard Objective	Current	(unchanged)
0x4A 0x4B	Set Passengers	Current	(unchanged)
0x4B 0x4C	Teams	Current	(unchanged)
0x4C 0x4D	Update Score	Current	(unchanged)
0x4D 0x4E	Spawn Position	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	(unchanged)

New/modified data types

No changes so far.

Entity Metadata

Lots of shifts, of course

Living

Extends Entity.

Index	Type	Meaning		Default
7	Byte	Hand states, used to trigger blocking/eating/drinking animation.		0
		Bit mask	Meaning
		0x01	Is hand active
		0x02	Active hand (0 = main hand, 1 = offhand)
		0x04	In riptide spin attack
8	Float	Health		1.0
9	VarInt	Potion effect color (or 0 if there is no effect)		0
10	Boolean	Is potion effect ambient: reduces the number of particles generated by potions to 1/5 the normal amount		false
11	VarInt	Number of arrows in entity		0
12	VarInt	Unknown		0
12 13	OptBlockPos	Unknown (Bed location?)		Absent

Bee

Extends Insentient.

Index	Type	Meaning		Default
16	Byte	Unknown		0
17	VarInt	Unknown		0

Enderman

Extends Monster.

Index	Type	Meaning		Default
15	Opt BlockID	Carried block		Absent
16	Boolean	Is screaming		false
17	Boolean	Unknown		false

Block Actions

No changes so far.

Inventories

No changes so far.

Plugin Channels

No changes so far.

Play

Clientbound

Spawn Mob

Sent by the server when a mob entity is spawned.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x03	Play	Client	Entity ID	VarInt
			Entity UUID	UUID
			Type	VarInt	The type of mob. See Entities#Mobs
			X	Double
			Y	Double
			Z	Double
			Yaw	Angle
			Pitch	Angle
			Head Pitch	Angle
			Velocity X	Short	Same units as Entity Velocity
			Velocity Y	Short	Same units as Entity Velocity
			Velocity Z	Short	Same units as Entity Velocity
			Metadata	Entity Metadata

Spawn Player

This packet is sent by the server when a player comes into visible range, not when a player joins.

This packet must be sent after the Player Info packet that adds the player data for the client to use when spawning a player. If the Player Info for the player spawned by this packet is not present when this packet arrives, Notchian clients will not spawn the player entity. The Player Info packet includes skin/cape data.

Servers can, however, safely spawn player entities for players not in visible range. The client appears to handle it correctly.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x05	Play	Client	Entity ID	VarInt	Player's EID
			Player UUID	UUID	See below for notes on offline mode and NPCs
			X	Double
			Y	Double
			Z	Double
			Yaw	Angle
			Pitch	Angle
			Metadata	Entity Metadata

When in online mode, the UUIDs must be valid and have valid skin blobs.

In offline mode, UUID v3 is used with the String OfflinePlayer:<player name>, encoded in UTF-8 (and case-sensitive).

For NPCs UUID v2 should be used. Note:

<+Grum> i will never confirm this as a feature you know that :)

In an example UUID, xxxxxxxx-xxxx-Yxxx-xxxx-xxxxxxxxxxxx, the UUID version is specified by Y. So, for UUID v3, Y will always be 3, and for UUID v2, Y will always be 2.

Update Block Entity

Sets the block entity associated with the block at the given location.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x09 0x0A	Play	Client	Location	Position
			Action	Unsigned Byte	The type of update to perform, see below
			NBT Data	NBT Tag	Data to set. May be a TAG_END (0), in which case the block entity at the given location is removed (though this is not required since the client will remove the block entity automatically on chunk unload or block removal)

Action field:

• 1: Set data of a mob spawner (everything except for SpawnPotentials: current delay, min/max delay, mob to be spawned, spawn count, spawn range, etc.)
• 2: Set command block text (command and last execution status)
• 3: Set the level, primary, and secondary powers of a beacon
• 4: Set rotation and skin of mob head
• 5: Declare a conduit
• 6: Set base color and patterns on a banner
• 7: Set the data for a Structure tile entity
• 8: Set the destination for a end gateway
• 9: Set the text on a sign
• 10: Unused
• 11: Declare a bed
• 12: Set data of a jigsaw block
• 13: Set items in a campfire
• 14: Beehive information

Chunk Data

Main article: Chunk Format

See also: #Unload Chunk

The server only sends skylight information for chunk pillars in the Overworld, it's up to the client to know in which dimenison the player is currently located. You can also infer this information from the primary bitmask and the amount of uncompressed bytes sent. This packet also sends all block entities in the chunk (though sending them is not required; it is still legal to send them with Update Block Entity later).

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x21 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).
			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	Optional array of Integer	1024 biome IDs, unknown order. 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.

Join Game

See Protocol Encryption for information on logging in.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x25 0x26	Play	Client	Entity ID	Int	The player's Entity ID (EID)
			Gamemode	Unsigned Byte	0: Survival, 1: Creative, 2: Adventure, 3: Spectator. Bit 3 (0x8) is the hardcore flag.
			Dimension	Int Enum	-1: Nether, 0: Overworld, 1: End; also, note that this is not a VarInt but instead a regular int.
			Unknown	Long	Unknown
			Max Players	Unsigned Byte	Was once used by the client to draw the player list, but now is ignored
			Level Type	String Enum (16)	default, flat, largeBiomes, amplified, customized, buffet, default_1_1
			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.
			Unknown	Boolean	Added

Respawn

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
0x3A 0x3B	Play	Client	Dimension	Int Enum	-1: The Nether, 0: The Overworld, 1: The End
			Unknown	Long	Unknown
			Gamemode	Unsigned Byte	0: survival, 1: creative, 2: adventure, 3: spectator. The hardcore flag is not included
			Level Type	String (16)	Same as Join Game

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).

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.

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 498 557)
			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.