Registries#

Minecraft 26.1.2 transmits a number of dynamic registries from the server to the client during the Configuration state. These registries describe data-driven content that the client must know about (biomes, dimension types, chat formatting, damage types, mob variants, paintings, enchantments, instruments, jukebox songs, dialogs, etc.) and that the server may have customized via data packs.

This page specifies how the dynamic registry sync works on the wire, the bootstrap "Known Packs" handshake, the list of registries that participate, and the NBT shape of the most important entries.

Mechanism#

Dynamic registries are synchronized after Login and before Play, while the connection is in the Configuration state. The server sends one Registry Data packet per registry to be synchronized. Each packet carries:

Field	Type	Notes
Registry ID	Identifier	The registry being transmitted (e.g. minecraft:worldgen/biome).
Entries	Array of ([Identifier](./data-types#identifier), Optional [NBT](./data-types#nbt))	Every entry the client should add to that registry.

Each entry contains:

Field	Type	Notes
Entry ID	Identifier	The registry-key for the entry (e.g. minecraft:plains).
Has data	Boolean	Whether the NBT payload follows.
Data	NBT (network NBT, no name)	Only present when Has data = true.

If Has data is false, the client uses its own built-in vanilla copy of that entry as supplied by the matching known pack. If Has data is true, the supplied NBT replaces (or defines) the entry.

The order of Registry Data packets is significant: they must be received before Update Tags (see ./tags) for the same registries, and before Finish Configuration.

Known Packs handshake#

Before sending any Registry Data, the server sends Select Known Packs (clientbound). The client replies with Select Known Packs (serverbound) listing the data packs it already knows. A pack is identified by:

Field	Type	Notes
Namespace	String	Pack namespace; vanilla uses "minecraft".
ID	String	Pack identifier (e.g. "core").
Version	String	Pack version, typically the game version (e.g. "1.21.10").

For every entry in a registry that comes from a pack the client claims to have, the server is allowed to omit the NBT payload (Has data = false) and rely on the client to materialize the entry locally. In practice this means a vanilla client that reports the minecraft:core pack only receives NBT for non-vanilla entries, drastically reducing bandwidth at login.

If the client claims no packs, every entry must be sent with full NBT.

Synchronized registries#

The set of registries that must be sent (when their entries are not entirely covered by known packs) is:

• minecraft:worldgen/biome
• minecraft:chat_type
• minecraft:trim_pattern
• minecraft:trim_material
• minecraft:wolf_variant
• minecraft:wolf_sound_variant
• minecraft:pig_variant
• minecraft:pig_sound_variant
• minecraft:frog_variant
• minecraft:cat_variant
• minecraft:cat_sound_variant
• minecraft:cow_variant
• minecraft:cow_sound_variant
• minecraft:chicken_variant
• minecraft:chicken_sound_variant
• minecraft:zombie_nautilus_variant
• minecraft:painting_variant
• minecraft:dimension_type
• minecraft:damage_type
• minecraft:banner_pattern
• minecraft:enchantment
• minecraft:jukebox_song
• minecraft:instrument
• minecraft:test_environment
• minecraft:test_instance
• minecraft:dialog
• minecraft:world_clock
• minecraft:timeline

Other registries (blocks, items, entity types, fluids, particles, sound events, recipes, etc.) are not transmitted because their IDs are part of the protocol contract for a given version and are baked into the client.

Entry NBT schemas#

The NBT schema is the network codec of each registry's element (which can differ from its on-disk codec; some fields are stripped because they are server-only).

minecraft:worldgen/biome#

Field	Type	Notes
attributes	Compound (optional)	Environment attribute overrides; defaults to empty.
effects	Compound	Visual/audio effects: fog_color, water_color, water_fog_color, sky_color, optional foliage_color, grass_color, optional grass_color_modifier, optional particle, optional ambient_sound, optional mood_sound, optional additions_sound, optional music.

The non-network (data-pack) codec also has has_precipitation, temperature, temperature_modifier, downfall, spawners, spawn_costs, carvers, and features, but these are not sent over the wire.

minecraft:dimension_type#

Field	Type	Notes
has_fixed_time	Boolean (optional, default false)	If true, time is fixed at fixed_time.
fixed_time	Long (optional)	Daytime tick when has_fixed_time is true.
has_skylight	Boolean	Whether the dimension has skylight.
has_ceiling	Boolean	Whether the dimension has a solid ceiling (Nether).
has_ender_dragon_fight	Boolean	Whether to spawn the dragon fight.
coordinate_scale	Double	Coordinate scaling factor (Nether = 8.0).
min_y	Int	Minimum world Y.
height	Int	Total Y range (multiple of 16).
logical_height	Int	Maximum Y for portals/teleporters.
infiniburn	Identifier	Tag (#namespace:path) of always-burning blocks.
ambient_light	Float	Constant added to computed light.
monster_settings	Compound	monster_spawn_light_level (int provider) + monster_spawn_block_light_limit (int 0–15).
skybox	Compound (optional)	Sky rendering preset.
cardinal_light	String enum (optional)	Cardinal light type.
attributes	Compound (optional)	Environment attribute overrides.
timelines	Holder set (optional)	List/tag of timeline references.
default_clock	Compound (optional)	World clock override.

minecraft:chat_type#

Field	Type	Notes
chat	Compound	Decoration applied to in-chat rendering.
narration	Compound	Decoration applied to narration.

Each decoration has:

Field	Type	Notes
translation_key	String	Translation key, e.g. "chat.type.text".
parameters	List of String	Ordered list of parameter names ("sender", "target", "content").
style	Compound (optional)	Text style applied to the rendered output.

See ./chat for how chat types are bound to messages.

minecraft:damage_type#

Field	Type	Notes
message_id	String	Translation key suffix used by death messages.
scaling	String enum	"never", "when_caused_by_living_non_player", or "always".
exhaustion	Float	Hunger exhaustion induced.
effects	String enum (optional)	Hurt sound class: "hurt", "thorns", "drowning", "burning", "poking", "freezing". Default "hurt".
death_message_type	String enum (optional)	"default", "fall_variants", "intentional_game_design".

minecraft:painting_variant#

Field	Type	Notes
asset_id	Identifier	Texture identifier.
width	Int (1–16)	Painting width in blocks.
height	Int (1–16)	Painting height in blocks.
title	Component (optional)	Display title.
author	Component (optional)	Display author.

minecraft:wolf_variant (and other mob variants)#

The mob-variant registries (wolf_variant, cat_variant, frog_variant, pig_variant, cow_variant, chicken_variant, zombie_nautilus_variant) all follow the same shape over the wire — they reduce to a list of model assets:

Field	Type	Notes
assets	Compound	Asset references for the model variant; structure is variant-specific (e.g. wolf has wild, tame, angry).

The data-pack form additionally carries a spawn_conditions list and biome tag, but those are server-only and not in the network codec.

minecraft:enchantment#

Field	Type	Notes
description	Component	Display name.
exclusive_set	Holder set (optional)	Items mutually exclusive with this enchantment.
supported_items	Holder set	Items that may carry this enchantment.
primary_items	Holder set (optional)	Items eligible from the table.
weight	Int	Selection weight.
max_level	Int	Maximum level.
min_cost / max_cost	Compound	Anvil/table cost ranges.
anvil_cost	Int	Combine cost.
slots	List of String	Equipment slots in which the enchantment is active.
effects	Compound	Component-style effect map.

minecraft:jukebox_song#

Field	Type	Notes
sound_event	Holder/Identifier	Sound to play; either a registry holder or inline SoundEvent.
description	Component	Display name shown in the jukebox tooltip.
length_in_seconds	Float	Track length.
comparator_output	Int (0–15)	Redstone signal strength.

minecraft:instrument#

Field	Type	Notes
sound_event	Holder/Identifier	Sound emitted when used.
use_duration	Float	Use animation duration in seconds.
range	Float	Audible range in blocks.
description	Component	Display name.

minecraft:trim_pattern / minecraft:trim_material#

trim_pattern:

Field	Type	Notes
asset_id	Identifier	Texture identifier.
description	Component	Display name (used in tooltip).
decal	Boolean	Whether the trim is rendered as a decal.

trim_material:

Field	Type	Notes
assets	Compound	Per-armor-material override map.
description	Component	Tooltip display component.

minecraft:banner_pattern#

Field	Type	Notes
asset_id	Identifier	Texture identifier.
translation_key	String	Translation key for the tooltip.

minecraft:dialog#

A self-contained UI dialog definition (introduced in 1.21.6+). The schema is large and deeply nested (buttons, body items, action lists). Treat the payload as an opaque NBT compound on the wire and decode it with the dialog codec.

minecraft:test_environment and minecraft:test_instance#

Game-test definitions used by the /test command. Sent for parity with the integrated server and may be empty in production deployments.

NOTE: For registries whose network codec equals their data codec (DIRECT_CODEC), the on-disk JSON shape under data/<namespace>/<registry path>/ translates field-for-field into the wire NBT.

Source: net/minecraft/resources/RegistryDataLoader.java, net/minecraft/core/RegistrySynchronization.java, net/minecraft/core/registries/Registries.java, net/minecraft/network/protocol/configuration/ClientboundRegistryDataPacket.java, net/minecraft/network/protocol/configuration/ClientboundSelectKnownPacks.java, net/minecraft/network/protocol/configuration/ServerboundSelectKnownPacks.java, net/minecraft/server/packs/repository/KnownPack.java, net/minecraft/world/level/biome/Biome.java, net/minecraft/world/level/dimension/DimensionType.java, net/minecraft/network/chat/ChatType.java, net/minecraft/world/damagesource/DamageType.java, net/minecraft/world/entity/decoration/PaintingVariant.java, net/minecraft/world/item/enchantment/Enchantment.java, net/minecraft/world/item/JukeboxSong.java, net/minecraft/world/item/Instrument.java.