Difference between revisions of "Pre-release protocol"

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* For {{change||block states and }}bits per {{change|block|entry}} <= 4, 4 bits are used to represent a block.
* For {{change||block states and }}bits per block between 5 and 8, the given value is used.
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* For {{change||block states and }}bits per {{change|block|entry}} between 5 and 8, the given value is used.
 
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Revision as of 23:36, 30 November 2021

This page documents the changes from the last stable Minecraft release (currently 1.17.1, protocol 756) to the current pre-release (currently 1.18-rc1, protocol Snapshot 57). 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

Packets

ID Packet name Documentation
Play clientbound
0x0A Block Entity Data Current Pre
0x22 Chunk Data and Update Light Current Pre
0x26 Join Game Current Pre
0x57 Update Simulation Distance Pre
0x57 0x58 Set Title SubTitle Current (unchanged)
0x58 0x59 Time Update Current (unchanged)
0x59 0x5A Set Title Text Current (unchanged)
0x5A 0x5B Set Title Times Current (unchanged)
0x5B 0x5C Entity Sound Effect Current (unchanged)
0x5C 0x5D Sound Effect Current (unchanged)
0x5D 0x5E Stop Sound Current (unchanged)
0x5E 0x5F Player List Header And Footer Current (unchanged)
0x5F 0x60 NBT Query Response Current (unchanged)
0x60 0x61 Collect Item Current (unchanged)
0x61 0x62 Entity Teleport Current (unchanged)
0x62 0x63 Advancements Current (unchanged)
0x63 0x64 Entity Properties Current (unchanged)
0x64 0x65 Entity Effect Current (unchanged)
0x65 0x66 Declare Recipes Current (unchanged)
0x66 0x67 Tags Current (unchanged)
Play serverbound
0x05 Client Settings Current Pre


New/modified data types

Chunk Section

The data section of the packet contains most of the useful data for the chunk.

Field Name Field Type Notes
Data Array of Chunk Section The number of elements in the array is equal to the number of bits set in Primary Bit Mask calculated based on the world's height. Sections are sent bottom-to-top, i.e. the first section, if sent, extends from Y=0 to Y=15.

Chunk Section structure

A Chunk Section is defined in terms of other data types. A Chunk Section consists of the following fields:

Field Name Field Type Notes
Block count Short Number of non-air blocks present in the chunk section. "Non-air" is defined as any block other than air, cave air, and void air (in particular, note that fluids such as water are still counted). The client uses this to unload chunks empty chunks. It will keep count of the blocks as they are broken/placed and if this integer reaches 0 the whole chunk section is not rendered, even though there may still be blocks left, if the server sends an incorrect block count.
Bits Per Block Unsigned Byte Determines how many bits are used to encode a block. Note that not all numbers are valid here.
Palette Varies See below for the format.
Data Array Length VarInt Number of longs in the following array
Data Array Array of Long Compacted list of 4096 (16x16x16) indices pointing to state IDs in the Palette (see Compacted data array)
Block states Paletted Container Consists of 4096 entries, representing all the blocks in the chunk section
Biomes Paletted Container Consists of 64 entries, representing 4x4x4 biome regions in the chunk section

Paletted Container structure

A Paletted Container is a palette-based storage of entries. Paletted Containers have an associated global palette (either block states or biomes as of now), where values are mapped from. A Paletted Container consists of the following fields:

Field Name Field Type Notes
Bits Per Entry Unsigned Byte Determines how many bits are used to encode entries. Note that not all numbers are valid here.
Palette Varies See below for the format.
Data Array Length VarInt Number of longs in the following array
Data Array Array of Long Compacted list of indices pointing to entry IDs in the Palette. When Bits Per Entry is 0, this array is empty (see Single valued palette)

Data Array is given for each entry with increasing x coordinates, within rows of increasing z coordinates, within layers of increasing y coordinates.

Palettes

The bits per block entry value determines what format is used for the palette. In most cases, invalid values will be interpreted as a different value when parsed by the notchian client, meaning that chunk data will be parsed incorrectly if you use an invalid bits per block entry. Servers must make sure that the bits per block entry value is correct. There are currently three types of palettes:

Single valued

This format is used when bits per entry is equal to 0, and signifies that the palette contains a single value. When this palette is used, the Data Array sent/received is empty, since entries can be inferred from the palette's single value.

The format is as follows:

Field Name Field Type Notes
Value VarInt ID of the corresponding entry in its global palette
Indirect

There are two three variants of this:

  • For block states and bits per block entry <= 4, 4 bits are used to represent a block.
  • For block states and bits per block entry between 5 and 8, the given value is used.
  • For biomes and bits per entry <= 3, the given value is used.

This is an actual palette which lists the block states entries used. Values in the chunk section's data array are indices into the palette, which in turn gives a proper block state entry.

The format is as follows:

Field Name Field Type Notes
Palette Length VarInt Number of elements in the following array.
Palette Array of VarInt Mapping of block state entry IDs in the global palette to indices of this array
Direct

This format is used for bits per block entry values greater than or equal to 9 a threshold (9 for block states, 4 for biomes). The number of bits used to represent a block an entry is the base 2 logarithm of the number of block states entries in the global palette, rounded up. For the current vanilla release, this is 15 bits per block per entry for block states, and 6 bits per entry for biomes.

The "palette" uses the following format:

Field Name Field Type Notes
no fields

Entity Metadata

No changes so far.

Entity

No changes so far.

Block Actions

No changes so far.

Inventories

No changes so far.

Plugin Channels

No changes so far.

Play

Clientbound

Block Entity Data

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

Packet ID State Bound To Field Name Field Type Notes
0x0A Play Client Location Position
Action Unsigned Byte The type of update to perform, see below.
Type VarInt The type of block entity
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).

Chunk Data and Update Light

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). See Light for information on how lighting works in Minecraft.

Packet ID State Bound To Field Name Field Type Notes
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)
Primary Bit Mask BitSet BitSet of length world height in chunk sections, i.e. height / 16. Bits are 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 , with the number of bits per entry varying depending on the world's height, defined by the formula ceil(log2(height + 1))). 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; should always be 1024. 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. Not present if full chunk is false. See Chunk Format § Biomes.
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.
Block Entity Packed XZ Array Byte The packed section coordinates, calculated from ((blockX & 15) << 4) | (blockZ & 15)
Y Short The height relative to the world
Type VarInt The type of block entity
Data NBT The block entity's data, without the X, Y, and Z values
Trust Edges Boolean If edges should be trusted for light updates.
Sky Light Mask BitSet BitSet containing bits for each section in the world + 2. Each set bit indicates that the corresponding 16×16×16 chunk section has data in the Sky Light array below. The least significant bit is for blocks 16 blocks to 1 block below the min world height (one section below the world), while the most significant bit covers blocks 1 to 16 blocks above the max world height (one section above the world).
Block Light Mask BitSet BitSet containing bits for each section in the world + 2. Each set bit indicates that the corresponding 16×16×16 chunk section has data in the Block Light array below. The order of bits is the same as in Sky Light Mask.
Empty Sky Light Mask BitSet BitSet containing bits for each section in the world + 2. Each set bit indicates that the corresponding 16×16×16 chunk section has all zeros for its Sky Light data. The order of bits is the same as in Sky Light Mask.
Empty Block Light Mask BitSet BitSet containing bits for each section in the world + 2. Each set bit indicates that the corresponding 16×16×16 chunk section has all zeros for its Block Light data. The order of bits is the same as in Sky Light Mask.
Sky Light array count VarInt Number of entries in the following array; should match the number of bits set in Sky Light Mask
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; should match the number of bits set in Block Light Mask
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.

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

A bit will never be set in both the block light mask and the empty block light mask, though it may be present in neither of them (if the block light does not need to be updated for the corresponding chunk section). The same applies to the sky light mask and the empty sky light mask.

Join Game

See Protocol Encryption for information on logging in.

Packet ID State Bound To Field Name Field Type Notes
0x26 Play Client Entity ID Int The player's Entity ID (EID).
Is hardcore Boolean
Gamemode Unsigned Byte 0: Survival, 1: Creative, 2: Adventure, 3: Spectator.
Previous Gamemode Byte 0: survival, 1: creative, 2: adventure, 3: spectator. The hardcore flag is not included. The previous gamemode. Defaults to -1 if there is no previous gamemode. (More information needed)
World Count VarInt Size of the following array.
World Names Array of Identifier Identifiers for all worlds on the server.
Dimension Codec NBT Tag Compound The full extent of these is still unknown, but the tag represents a dimension and biome registry. See below for the vanilla default.
Dimension NBT Tag Compound Valid dimensions are defined per dimension registry sent before this. The structure of this tag is a dimension type (see below).
World Name Identifier Name of the world 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.
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.


The Dimension Codec NBT Tag Compound (Default value in SNBT) includes two registries: "minecraft:dimension_type" and "minecraft:worldgen/biome".

Name Type Notes
minecraft:dimension_type TAG_Compound The dimension type registry (see below).
minecraft:worldgen/biome TAG_Compound The biome 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.
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.
has_raids TAG_Byte Whether players with the Bad Omen effect can cause a raid. 1: true, 0: false.
min_y TAG_Int The minimum Y level.
height TAG_Int The maximum height.
logical_height TAG_Int The maximum height to which chorus fruits and nether portals can bring players within this dimension. 0-256.
coordinate_scale TAG_Float 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
precipitation TAG_String The type of precipitation in the biome. "rain", "snow", or "none".
depth 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 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 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.

Update Simulation Distance

Packet ID State Bound To Field Name Field Type Notes
0x26 Play Client Simulation Distance VarInt The distance that the client will process specific things, such as entities.

Serverbound

Client Settings

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

Packet ID State Bound To Field Name Field Type Notes
0x05 Play 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.
Displayed Skin Parts Unsigned Byte Bit mask, see below.
Main Hand VarInt Enum 0: Left, 1: Right.
Disable text filtering Boolean Disables filtering of text on signs and written book titles. Currently always true (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.

Status

Clientbound

No changes so far.

Serverbound

No changes so far.

Login

Clientbound

No changes so far.

Serverbound

No changes so far.