Pre-release protocol

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Revision as of 15:38, 18 September 2023 by WinX64 (talk | contribs) (1.20.2-rc2)
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This page documents the changes from the last stable Minecraft release (currently 1.20.1, protocol 763) to the current pre-release (currently 1.20.2-rc2, protocol Snapshot 153). 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

NBT

Root NBT Tags are now always nameless. Below is an example of the resulting bytes from an encoded CompoundTag containing an IntTag(42) named test. 

  0A 00 00 03 00 04 74 65 73 74 00 00 00 2A 00 | Before
  0A       03 00 04 74 65 73 74 00 00 00 2A 00 | Now

This affects all packets and data types containing NBT Tag fields:

Packets

ID Packet name Documentation
Login clientbound
0x02 Login Success Current Pre
Login serverbound
0x00 Login Start Current Pre
0x03 Login Acknowledged Pre
Configuration clientbound
0x00 Plugin Message (configuration) Pre
0x01 Disconnect (configuration) Pre
0x02 Finish Configuration Pre
0x03 Keep Alive (configuration) Pre
0x04 Ping (configuration) Pre
0x05 Registry Data Pre
0x06 Resource Pack (configuration) Pre
0x07 Feature Flags Pre
0x08 Update Tags Pre
Configuration serverbound
0x00 Client Information (configuration) Pre
0x01 Plugin Message (configuration) Pre
0x02 Finish Configuration Pre
0x03 Keep Alive (configuration) Pre
0x04 Pong (configuration) Pre
0x05 Resource Pack Pre
Play clientbound
0x03 Spawn Player Current
0x04 0x03 Entity Animation Current (unchanged)
0x05 0x04 Award Statistics Current (unchanged)
0x06 0x05 Acknowledge Block Change Current (unchanged)
0x07 0x06 Set Block Destroy Stage Current (unchanged)
0x08 0x07 Block Entity Data Current (unchanged)
0x09 0x08 Block Action Current (unchanged)
0x0A 0x09 Block Update Current (unchanged)
0x0B 0x0A Boss Bar Current (unchanged)
0x0C 0x0B Change Difficulty Current (unchanged)
0x0C Chunk Batch Finished Pre
0x0D Chunk Batch Start Pre
0x0D 0x0E Chunk Biomes Current (unchanged)
0x0E 0x0A Clear Titles Current (unchanged)
0x0F 0x10 Command Suggestions Response Current (unchanged)
0x10 0x11 Commands Current (unchanged)
0x11 0x12 Close Container Current (unchanged)
0x12 0x13 Set Container Content Current (unchanged)
0x13 0x14 Set Container Property Current (unchanged)
0x14 0x15 Set Container Slot Current (unchanged)
0x15 0x16 Set Cooldown Current (unchanged)
0x16 0x17 Chat Suggestions Current (unchanged)
0x17 0x18 Plugin Message Current (unchanged)
0x18 0x19 Damage Event Current (unchanged)
0x19 0x1A Delete Message Current (unchanged)
0x1A 0x1B Disconnect (play) Current (unchanged)
0x1B 0x1C Disguised Chat Message Current (unchanged)
0x1C 0x1D Entity Event Current (unchanged)
0x1D 0x1E Explosion Current (unchanged)
0x1E 0x1F Unload Chunk Current (unchanged)
0x1F 0x20 Game Event Current (unchanged)
0x20 0x21 Open Horse Screen Current (unchanged)
0x21 0x22 Hurt Animation Current (unchanged)
0x22 0x23 Initialize World Border Current (unchanged)
0x23 0x24 Keep Alive Current (unchanged)
0x24 0x25 Chunk Data and Update Light Current (unchanged)
0x25 0x26 World Event Current (unchanged)
0x26 0x27 Particle Current (unchanged)
0x27 0x28 Update Light Current (unchanged)
0x28 0x29 Login (play) Current Pre
0x29 0x2A Map Data Current (unchanged)
0x2A 0x2B Merchant Offers Current (unchanged)
0x2B 0x2C Update Entity Position Current (unchanged)
0x2C 0x2D Update Entity Position and Rotation Current (unchanged)
0x2D 0x2E Update Entity Rotation Current (unchanged)
0x2E 0x2F Move Vehicle Current (unchanged)
0x2F 0x30 Open Book Current (unchanged)
0x30 0x31 Open Screen Current (unchanged)
0x31 0x32 Open Sign Editor Current (unchanged)
0x32 0x33 Ping (play) Current (unchanged)
0x34 Ping Response (play) Pre
0x33 0x35 Place Ghost Recipe Current (unchanged)
0x34 0x36 Player Abilities Current (unchanged)
0x35 0x37 Player Chat Message Current (unchanged)
0x36 0x38 End Combat Current (unchanged)
0x37 0x39 Enter Combat Current (unchanged)
0x38 0x3A Combat Death Current (unchanged)
0x39 0x3B Player Info Remove Current (unchanged)
0x3A 0x3C Player Info Update Current (unchanged)
0x3B 0x3D Look At Current (unchanged)
0x3C 0x3E Synchronize Player Position Current (unchanged)
0x3D 0x3F Update Recipe Book Current (unchanged)
0x3E 0x40 Remove Entities Current (unchanged)
0x3F 0x41 Remove Entity Effect Current (unchanged)
0x40 0x42 Resource Pack Current (unchanged)
0x41 0x43 Respawn Current Pre
0x42 0x44 Set Head Rotation Current (unchanged)
0x43 0x45 Update Section Blocks Current (unchanged)
0x44 0x46 Select Advancements Tab Current (unchanged)
0x45 0x47 Server Data Current (unchanged)
0x46 0x48 Set Action Bar Text Current (unchanged)
0x47 0x49 Set Border Center Current (unchanged)
0x48 0x4A Set Border Lerp Size Current (unchanged)
0x49 0x4B Set Border Size Current (unchanged)
0x4A 0x4C Set Border Warning Delay Current (unchanged)
0x4B 0x4D Set Border Warning Distance Current (unchanged)
0x4C 0x4E Set Camera Current (unchanged)
0x4D 0x4F Set Held Item Current (unchanged)
0x4E 0x50 Set Center Chunk Current (unchanged)
0x4F 0x51 Set Render Distance Current (unchanged)
0x50 0x52 Set Default Spawn Position Current (unchanged)
0x51 0x53 Display Objective Current Pre
0x52 0x54 Set Entity Metadata Current (unchanged)
0x53 0x55 Link Entities Current (unchanged)
0x54 0x56 Set Entity Velocity Current (unchanged)
0x55 0x57 Set Equipment Current (unchanged)
0x56 0x58 Set Experience Current (unchanged)
0x57 0x59 Set Health Current (unchanged)
0x58 0x5A Update Objectives Current (unchanged)
0x59 0x5B Set Passengers Current (unchanged)
0x5A 0x5C Update Teams Current (unchanged)
0x5B 0x5D Update Score Current (unchanged)
0x5C 0x5E Set Simulation Distance Current (unchanged)
0x5D 0x5F Set Subtitle Text Current (unchanged)
0x5E 0x60 Update Time Current (unchanged)
0x5F 0x61 Set Title Text Current (unchanged)
0x60 0x62 Set Title Animation Times Current (unchanged)
0x61 0x63 Entity Sound Effect Current (unchanged)
0x62 0x64 Sound Effect Current (unchanged)
0x65 Start Configuration Pre
0x63 0x66 Stop Sound Current (unchanged)
0x64 0x67 System Chat Message Current (unchanged)
0x65 0x68 Set Tab List Header And Footer Current (unchanged)
0x66 0x69 Tag Query Response Current (unchanged)
0x67 0x6A Pickup Item Current (unchanged)
0x68 0x6B Teleport Entity Current (unchanged)
0x69 0x6C Update Advancements Current Pre
0x6A 0x6D Update Attributes Current (unchanged)
0x6B Feature Flags Current
0x6C 0x6E Entity Effect Current (unchanged)
0x6D 0x6F Update Recipes Current (unchanged)
0x6E 0x70 Update Tags Current (unchanged)
Play serverbound
0x07 Chunk Batch Received Pre
0x07 0x08 Client Command Current (unchanged)
0x08 0x09 Client Information Current (unchanged)
0x09 0x0A Command Suggestions Request Current (unchanged)
0x0B Configuration Acknowledged Pre
0x0A 0x0C Click Container Button Current (unchanged)
0x0B 0x0D Click Container Current (unchanged)
0x0C 0x0E Close Container Current (unchanged)
0x0D 0x0F Plugin Message Current (unchanged)
0x0E 0x10 Edit Book Current (unchanged)
0x0F 0x11 Query Entity Tag Current (unchanged)
0x10 0x12 Interact Current (unchanged)
0x11 0x13 Jigsaw Generate Current (unchanged)
0x12 0x14 Keep Alive Current (unchanged)
0x13 0x15 Lock Difficulty Current (unchanged)
0x14 0x16 Set Player Position Current (unchanged)
0x15 0x17 Set Player Position and Rotation Current (unchanged)
0x16 0x18 Set Player Rotation Current (unchanged)
0x17 0x19 Set Player On Ground Current (unchanged)
0x18 0x1A Move Vehicle Current (unchanged)
0x19 0x1B Paddle Boat Current (unchanged)
0x1A 0x1C Pick Item Current (unchanged)
0x1D Ping Request (play) Pre
0x1B 0x1E Place Recipe Current (unchanged)
0x1C 0x1F Player Abilities Current (unchanged)
0x1D 0x20 Player Action Current (unchanged)
0x1E 0x21 Player Command Current (unchanged)
0x1F 0x22 Player Input Current (unchanged)
0x20 0x23 Pong (play) Current (unchanged)
0x21 0x24 Change Recipe Book Settings Current (unchanged)
0x22 0x25 Set Seen Recipe Current (unchanged)
0x23 0x26 Rename Item Current (unchanged)
0x24 0x27 Resource Pack Current (unchanged)
0x25 0x28 Seen Advancements Current (unchanged)
0x26 0x29 Select Trade Current (unchanged)
0x27 0x2A Set Beacon Effect Current (unchanged)
0x28 0x2B Set Held Item Current (unchanged)
0x29 0x2C Program Command Block Current (unchanged)
0x2A 0x2D Program Command Block Minecart Current (unchanged)
0x2B 0x2E Set Creative Mode Slot Current (unchanged)
0x2C 0x2F Program Jigsaw Block Current (unchanged)
0x2D 0x30 Program Structure Block Current (unchanged)
0x2E 0x31 Update Sign Current (unchanged)
0x2F 0x32 Swing Arm Current (unchanged)
0x30 0x33 Teleport To Entity Current (unchanged)
0x31 0x34 Use Item On Current (unchanged)
0x32 0x35 Use Item Current (unchanged)

New/modified data types

No changes so far.

Entity Metadata

Display

Extends Entity.

Index Type Meaning Default
8 VarInt Interpolation delay 0
9 VarInt Interpolation Duration 0
9 VarInt Transformation interpolation duration 0
10 VarInt Position/Rotation interpolation duration 0
10 11 Vector3 Translation (0.0, 0.0, 0.0)
11 12 Vector3 Scale (1.0, 1.0, 1.0)
12 13 Quaternion Rotation left (0.0, 0.0, 0.0, 1.0)
13 14 Quaternion Rotation right (0.0, 0.0, 0.0, 1.0)
14 15 Byte Billboard Constraints (0 = FIXED, 1 = VERTICAL, 2 = HORIZONTAL, 3 = CENTER) 0
15 16 VarInt Brightness override (blockLight << 4 | skyLight << 20) -1
16 17 Float View range 1.0
17 18 Float Shadow radius 0.0
18 19 Float Shadow strength 1.0
19 20 Float Width 0.0
20 21 Float Height 0.0
21 22 VarInt Glow color override -1

Block Display

Extends Display.

Index Type Meaning Default
22 23 BlockID Displayed block state 0 (Air)

Item Display

Extends Display.

Index Type Meaning Default
22 23 Slot Displayed item Empty
23 24 Byte Display type:
  • 0 = NONE
  • 1 = THIRD_PERSON_LEFT_HAND
  • 2 = THIRD_PERSON_RIGHT_HAND
  • 3 = FIRST_PERSON_LEFT_HAND
  • 4 = FIRST_PERSON_RIGHT_HAND
  • 5 = HEAD
  • 6 = GUI
  • 7 = GROUND
  • 8 = FIXED
 0 (NONE)

Text Display

Extends Display.

Index Type Meaning Default
22 23 Chat Text Empty
23 24 VarInt Line width 200
24 25 VarInt Background color 1073741824 (0x40000000)
25 26 Byte Text opacity -1 (fully opaque)
26 27 Byte Bit mask Meaning 0
0x01 Has shadow
0x02 Is see through
0x04 Use default background color
0x08 Alignment:
  • 0 = CENTER
  • 1 or 3 = LEFT
  • 2 = RIGHT

Block Actions

No changes so far.

Inventories

No changes so far.

Plugin Channels

No changes so far.

Play

Clientbound

Chunk Batch Finished

Huh.png The following information needs to be added to this page:
Why does the formula uses 25 instead of the normal tick duration of 50?

Marks the end of a chunk batch. The Notchian client marks the time it receives this packet and calculates the ellapsed duration since the beggining of the chunk batch. The server uses this duration and the batch size received in this packet to estimate the number of milliseconds ellapsed per chunk received. This value is then used to calculate the desired number of chunks per tick through the formula 25 / millisPerChunk, which is reported to the server through Chunk Batch Received.

The Notchian client uses the samples from the latest 15 batches to estimate the milliseconds per chunk number.

Packet ID State Bound To Field Name Field Type Notes
0x0D Play Client Batch size VarInt Number of chunks.

Chunk Batch Start

Marks the start of a chunk batch. The Notchian client marks and stores the time it receives this packet.

Packet ID State Bound To Field Name Field Type Notes
0x0E Play Client no fields

Ping Response (play)

Packet ID State Bound To Field Name Field Type Notes
0x35 Play Client Payload Long Should be the same as sent by the client.


Login (play)

Huh.png The following information needs to be added to this page:
Although the number of portal cooldown ticks is included in this packet, the whole portal usage process is still dictated entirely by the server. What kind of effect does this value have on the client, if any?

See Protocol Encryption for information on logging in.

Packet ID State Bound To Field Name Field Type Notes
0x28 0x2A Play Client Entity ID Int The player's Entity ID (EID).
Is hardcore Boolean
Game mode Unsigned Byte 0: Survival, 1: Creative, 2: Adventure, 3: Spectator.
Previous Game mode Byte -1: Undefined (null), 0: Survival, 1: Creative, 2: Adventure, 3: Spectator. The previous game mode. Vanilla client uses this for the debug (F3 + N & F3 + F4) game mode switch. (More information needed)
Dimension Count VarInt Size of the following array.
Dimension Names Array of Identifier Identifiers for all dimensions on the server.
Registry Codec NBT Tag Compound Represents certain registries that are sent from the server and are applied on the client.
Dimension Type Identifier Name of the dimension type being spawned into.
Dimension Name Identifier Name of the dimension 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).
Simulation Distance VarInt The distance that the client will process specific things, such as entities.
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.
Do limited crafting Boolean Whether players can only craft recipes they have already unlocked. Currently unused by the client.
Dimension Type Identifier Name of the dimension type being spawned into.
Dimension Name Identifier Name of the dimension 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
Game mode Unsigned Byte 0: Survival, 1: Creative, 2: Adventure, 3: Spectator.
Previous Game mode Byte -1: Undefined (null), 0: Survival, 1: Creative, 2: Adventure, 3: Spectator. The previous game mode. Vanilla client uses this for the debug (F3 + N & F3 + F4) game mode switch. (More information needed)
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.
Has death location Boolean If true, then the next two fields are present.
Death dimension name Optional Identifier Name of the dimension the player died in.
Death location Optional Position The location that the player died at.
Portal cooldown VarInt The number of ticks until the player can use the portal again.

Respawn

Huh.png The following information needs to be added to this page:
Although the number of portal cooldown ticks is included in this packet, the whole portal usage process is still dictated entirely by the server. What kind of effect does this value have on the client, if any?

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
0x41 0x43 Play Client Dimension Type Identifier Valid dimensions are defined per dimension registry sent in Login (play)
Dimension Name Identifier Name of the dimension 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
Game mode Unsigned Byte 0: Survival, 1: Creative, 2: Adventure, 3: Spectator.
Previous Game mode Byte -1: Undefined (null), 0: Survival, 1: Creative, 2: Adventure, 3: Spectator. The previous game mode. Vanilla client uses this for the debug (F3 + N & F3 + F4) game mode switch. (More information needed)
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.
Data kept Byte Bit mask. 0x01: Keep attributes, 0x02: Keep metadata. Tells which data should be kept on the client side once the player has respawned.

In the Notchian implementation, this is context dependent:

  • normal respawns (after death) keep no data;
  • exiting the end poem/credits keeps the attributes;
  • other dimension changes (portals or teleports) keep all data.
Has death location Boolean If true, then the next two fields are present.
Death dimension Name Optional Identifier Name of the dimension the player died in.
Death location Optional Position The location that the player died at.
Portal cooldown VarInt The number of ticks until the player can use the portal again.
Data kept Byte Bit mask. 0x01: Keep attributes, 0x02: Keep metadata. Tells which data should be kept on the client side once the player has respawned.

In the Notchian implementation, this is context dependent:

  • normal respawns (after death) keep no data;
  • exiting the end poem/credits keeps the attributes;
  • other dimension changes (portals or teleports) keep all data.

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).

Before 1.16, 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.

Display Objective

This is sent to the client when it should display a scoreboard.

Packet ID State Bound To Field Name Field Type Notes
0x51 0x53 Play Client Position Byte VarInt The position of the scoreboard. 0: list, 1: sidebar, 2: below name, 3 - 18: team specific sidebar, indexed as 3 + team color.
Score Name String (32767) The unique name for the scoreboard to be displayed.

Start Configuration

Sent during gameplay in order to redo the configuration process. The client must respond with Configuration Acknowledged for the process to start.

Packet ID State Bound To Field Name Field Type Notes
0x65 Play Client no fields

This packet switches the connection state to configuration.

Feature Flags

Used to enable and disable features, generally experimental ones, on the client.

Packet ID State Bound To Field Name Field Type Notes
0x6B Play Client Total Features VarInt Number of features that appear in the array below.
Feature Flags Identifier Array

Update Advancements

Packet ID State Bound To Field Name Field Type Notes
0x69 0x6D Play Client Reset/Clear Boolean Whether to reset/clear the current advancements.
Mapping size VarInt Size of the following array.
Advancement mapping Key Array Identifier The identifier of the advancement.
Value Advancement See below
List size VarInt Size of the following array.
Identifiers Array of Identifier The identifiers of the advancements that should be removed.
Progress size VarInt Size of the following array.
Progress mapping Key Array Identifier The identifier of the advancement.
Value Advancement progress See below.

Advancement structure:

Field Name Field Type Notes
Has parent Boolean Indicates whether the next field exists.
Parent id Optional Identifier The identifier of the parent advancement.
Has display Boolean Indicates whether the next field exists.
Display data Optional advancement display See below.
Number of criteria VarInt Size of the following array.
Criteria Key Array Identifier The identifier of the criterion.
Value Void There is no content written here. Perhaps this will be expanded in the future?
Array length VarInt Number of arrays in the following array.
Requirements Array length 2 Array VarInt Number of elements in the following array.
Requirement Array of String (32767) Array of required criteria.
Sends telemetry data Boolean Whether the client should include this achievement in the telemetry data when it's completed.

The Notchian client only sends data for advancements on the minecraft namespace.

Advancement display:

Field Name Field Type Notes
Title Chat
Description Chat
Icon Slot
Frame type VarInt Enum 0 = task, 1 = challenge, 2 = goal.
Flags Int 0x01: has background texture; 0x02: show_toast; 0x04: hidden.
Background texture Optional Identifier Background texture location. Only if flags indicates it.
X coord Float
Y coord Float

Advancement progress:

Field Name Field Type Notes
Size VarInt Size of the following array.
Criteria Criterion identifier Array Identifier The identifier of the criterion.
Criterion progress Criterion progress

Criterion progress:

Field Name Field Type Notes
Achieved Boolean If true, next field is present.
Date of achieving Optional Long As returned by Date.getTime.

Serverbound

Chunk Batch Received

Notifies the server that the chunk batch has been received by the client. The server uses the value sent in this packet to adjust the number of chunks to be sent in a batch.

The Notchian server will stop sending further chunk data until the client acknowledges the sent chunk batch. After the first acknowledgement, the server adjusts this number to allow up to 10 unacknowledged batches.

Packet ID State Bound To Field Name Field Type Notes
0x07 Play Server Chunks per tick Float Desired chunks per tick.

Configuration Acknowledged

Sent by the client upon receiving a Start Configuration packet from the server.

Packet ID State Bound To Field Name Field Type Notes
0x0B Play Server no fields

This packet switches the connection state to configuration.

Ping Request (play)

Packet ID State Bound To Field Name Field Type Notes
0x1D Play Server Payload Long May be any number. Notchian clients use a system-dependent time value which is counted in milliseconds.

Status

Clientbound

No changes so far.

Serverbound

No changes so far.

Login

Clientbound

Login Success

Packet ID State Bound To Field Name Field Type Notes
0x02 Login Client UUID UUID
Username String (16)
Number Of Properties VarInt Number of elements in the following array.
Property Name Array String (32767)
Value String (32767)
Is Signed Boolean
Signature Optional String (32767) Only if Is Signed is true.

This packet switches the connection state to play configuration.

Serverbound

Login Start

Packet ID State Bound To Field Name Field Type Notes
0x00 Login Server Name String (16) Player's Username.
Has Player UUID Boolean Whether or not the next field should be sent.
Player UUID Optional UUID The UUID of the player logging in. Only sent if Has Player UUID is true.

Login Acknowledged

Acknowledgement to the Login Success packet sent by the server.

Packet ID State Bound To Field Name Field Type Notes
0x03 Login Server no fields

Configuration

Clientbound

Plugin Message (configuration)

Main article: Plugin channels

Mods and plugins can use this to send their data. Minecraft itself uses several plugin channels. These internal channels are in the minecraft namespace.

More information on how it works on Dinnerbone's blog. More documentation about internal and popular registered channels are here.

Packet ID State Bound To Field Name Field Type Notes
0x00 Configuration Client Channel Identifier Name of the plugin channel used to send the data.
Data Byte Array (1048576) Any data. The length of this array must be inferred from the packet length.

In Notchian client, the maximum data length is 1048576 bytes.

Disconnect (configuration)

Packet ID State Bound To Field Name Field Type Notes
0x01 Configuration Client Reason Chat The reason why the player was disconnected.

Finish Configuration

Sent by the server to notify the client that the configuration process has finished. The client answers with its own Finish Configuration whenever it is ready to continue.

Packet ID State Bound To Field Name Field Type Notes
0x02 Configuration Client no fields

This packet switches the connection state to play.

Keep Alive (configuration)

The server will frequently send out a keep-alive, each containing a random ID. The client must respond with the same payload (see serverbound Keep Alive). If the client does not respond to them for over 30 seconds, the server kicks the client. Vice versa, if the server does not send any keep-alives for 20 seconds, the client will disconnect and yields a "Timed out" exception.

The Notchian server uses a system-dependent time in milliseconds to generate the keep alive ID value.

Packet ID State Bound To Field Name Field Type Notes
0x03 Configuration Client Keep Alive ID Long

Ping (configuration)

Packet is not used by the Notchian server. When sent to the client, client responds with a Pong packet with the same id.

Packet ID State Bound To Field Name Field Type Notes
0x04 Configuration Client ID Int

Registry Data

Represents certain registries that are sent from the server and are applied on the client.

Packet ID State Bound To Field Name Field Type Notes
0x05 Configuration Client Registry Codec NBT Tag Compound Information included below.


The Registry Codec NBT Tag Compound (Default value in JSON as of 1.19, 1.19.2, 1.20.1) includes three registries: "minecraft:dimension_type", "minecraft:worldgen/biome", and "minecraft:chat_type".

Name Type Notes
minecraft:dimension_type TAG_Compound The dimension type registry (see below).
minecraft:worldgen/biome TAG_Compound The biome registry (see below).
minecraft:chat_type TAG_Compound The chat type 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.
has_raids TAG_Byte Whether players with the Bad Omen effect can cause a raid. 1: true, 0: false.
monster_spawn_light_level TAG_Int or TAG_Compound Possibly the light level(s) at which monsters can spawn. When TAG_Int, 0 - 15. When TAG_Compound, contains the fields: type (TAG_String), appears to be always "minecraft:uniform", and value (TAG_Compound), which contains the fields: max_inclusive (TAG_Int), min_inclusive (TAG_Int).
monster_spawn_block_light_limit TAG_Int
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.
min_y TAG_Int The minimum Y level. A multiple of 16. Example: -64
height TAG_Int The maximum height. A multiple of 16. Example: 256
logical_height TAG_Int The maximum height to which chorus fruits and nether portals can bring players within this dimension. (Must be lower than height) 0-384.
coordinate_scale TAG_Double The multiplier applied to coordinates when traveling to the dimension. 0.00001 - 30000000.0
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
has_precipitation TAG_Byte Determines whether or not the biome has precipitation. 1: true, 0: false.
depth Optional 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 Optional 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 Optional 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 probability Optional TAG_Compound TAG_FLOAT Particles that appear randomly in the biome. Possibly the probability of spawning the particle. ?
options TAG_COMPOUND The properties of the particle to spawn. Contains the field "type" (TAG_String), which identifies the particle type.

Chat registry:

Name Type Notes
type TAG_String The name of the registry. Always "minecraft:chat_type".
value TAG_List List of chat type registry entries (see below).

Chat type:

Name Type Notes
name TAG_String The type's name (eg "minecraft:chat")
id TAG_Int
elements TAG_Compound "chat" and "narration" TAG_Compound's (see below)

Chat type "chat" and "narration":

Name Type Notes
translation_key TAG_String
style TAG_Compound Similar to Chat JSON (only present in "chat" TAG_Compound)
parameters TAG_List of TAG_String Values can be "sender", "target" and "content"

Resource Pack

Packet ID State Bound To Field Name Field Type Notes
0x06 Configuration 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.
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.
Has Prompt Message Boolean true If the next field will be sent false otherwise. When false, this is the end of the packet
Prompt Message Optional Chat This is shown in the prompt making the client accept or decline the resource pack.

Feature Flags

Used to enable and disable features, generally experimental ones, on the client.

Packet ID State Bound To Field Name Field Type Notes
0x07 Configuration Client Total Features VarInt Number of features that appear in the array below.
Feature Flags Identifier Array

As of 1.20.2, the following feature flags are available:

  • minecraft:vanilla - enables vanilla features
  • minecraft:bundle - enables support for the bundle
  • minecraft:trade_rebalance - enables support for the rebalanced villager trades

Update Tags

Packet ID State Bound To Field Name Field Type Notes
0x08 Configuration Client 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.).

More information on tags is available at: https://minecraft.gamepedia.com/Tag

And a list of all tags is here: https://minecraft.gamepedia.com/Tag#List_of_tags

Serverbound

Client Information (configuration)

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

Packet ID State Bound To Field Name Field Type Notes
0x00 Configuration 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. Can the chat be colored?
Displayed Skin Parts Unsigned Byte Bit mask, see below.
Main Hand VarInt Enum 0: Left, 1: Right.
Enable text filtering Boolean Enables filtering of text on signs and written book titles. Currently always false (i.e. the filtering is disabled)
Allow server listings Boolean Servers usually list online players, this option should let you not show up in that list.

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.

Plugin Message (configuration)

Main article: Plugin channels

Mods and plugins can use this to send their data. Minecraft itself uses some plugin channels. These internal channels are in the minecraft namespace.

More documentation on this: https://dinnerbone.com/blog/2012/01/13/minecraft-plugin-channels-messaging/

Note that the length of Data is known only from the packet length, since the packet has no length field of any kind.

Packet ID State Bound To Field Name Field Type Notes
0x00 Configuration Server Channel Identifier Name of the plugin channel used to send the data.
Data Byte Array (32767) Any data, depending on the channel. minecraft: channels are documented here. The length of this array must be inferred from the packet length.

In Notchian server, the maximum data length is 32767 bytes.

Finish Configuration

Sent by the client to notify the client that the configuration process has finished. It is sent in response to the server's Finish Configuration.

Packet ID State Bound To Field Name Field Type Notes
0x01 Configuration Server no fields

This packet switches the connection state to play.

Keep Alive (configuration)

The server will frequently send out a keep-alive (see clientbound Keep Alive), each containing a random ID. The client must respond with the same packet.

Packet ID State Bound To Field Name Field Type Notes
0x02 Configuration Server Keep Alive ID Long

Pong (configuration)

Response to the clientbound packet (Ping) with the same id.

Packet ID State Bound To Field Name Field Type Notes
0x03 Configuration Server ID Int id is the same as the ping packet

Resource Pack (configuration)

Packet ID State Bound To Field Name Field Type Notes
0x04 Configuration Server Result VarInt Enum 0: successfully loaded, 1: declined, 2: failed download, 3: accepted.
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