Pre-release protocol

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This page documents the changes from the last stable Minecraft release (currently 1.16.4, protocol 754) to the current pre-release (currently 20w49a, protocol 1073741832). 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 Unknown 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 (unchanged)
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 (unchanged)
Handshaking serverbound
0x00 Handshake Current Pre

New/modified data types

No changes so far.

Entity Metadata

Warning.png 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

Unknown

Packet ID State Bound To Field Name Field Type Notes
0x05 Play Client Position Position
Identifier
Unknown Varies, may be a different data structure in different contexts
VarInt

Chunk Data

Main article: Chunk Format
See also: #Unload Chunk
Huh.png 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).
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. 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.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
Array 1 Array of Long Unknown
Length 2 VarInt Length of the following array
Array 2 Array of Long Unknown
Length 3 VarInt Length of the following array
Array 3 Array of Long Unknown
Length 4 VarInt Length of the following array
Array 4 Array of Long Unknown
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


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 ressource pack from the server. If they decline they will be kicked from the server.


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 1073741832)
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.