Pre-release protocol

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This page documents the changes from the last stable Minecraft release (currently 1.14.4, protocol 498) to the current pre-release (currently 19w36a, protocol 552). 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

Warning.png 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.
Unknown Int Array? An unknown number of integers, without an obvious length prefix?
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

Warning.png 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 498 552)
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.