minecraft_protocol/versions/1.13.md

1.13.x — Update Aquatic / The Flattening

Protocols: 393 (1.13), 401 (1.13.1), 404 (1.13.2) Release dates: 1.13 — 2018-07-18 · 1.13.1 — 2018-08-22 · 1.13.2 — 2018-10-22 Minecraft wiki release articles:

• https://minecraft.wiki/w/Java_Edition_1.13 (fetched 2026-06-19) — release date 2018-07-18, protocol 393, data version 1519, data/resource pack format 4
• https://minecraft.wiki/w/Java_Edition_1.13.1 (fetched 2026-06-19) — release date 2018-08-22, protocol 401
• https://minecraft.wiki/w/Java_Edition_1.13.2 (fetched 2026-06-19) — release date 2018-10-22, protocol 404 Protocol version numbers confirmed: ProtocolVersion.java lines 60-62 — register(393, "1.13"), register(401, "1.13.1"), register(404, "1.13.2") — /tmp/mcproto-refs/ViaVersion/api/src/main/java/com/viaversion/viaversion/api/protocol/version/ProtocolVersion.java; cross-checked against /tmp/mcproto-refs/minecraft-data/data/pc/1.13/version.json (393), 1.13.1/version.json (401), 1.13.2/version.json (404); confirmed on https://minecraft.wiki/w/Protocol_version (fetched 2026-06-19). ViaVersion packages:
• v1_12_2to1_13 — /tmp/mcproto-refs/ViaVersion/common/src/main/java/com/viaversion/viaversion/protocols/v1_12_2to1_13/
• v1_13to1_13_1 — …/protocols/v1_13to1_13_1/
• v1_13_1to1_13_2 — …/protocols/v1_13_1to1_13_2/ minecraft-data sources: data/pc/1.12.2/, data/pc/1.13/, data/pc/1.13.1/, data/pc/1.13.2/ — /tmp/mcproto-refs/minecraft-data/

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Headline changes — The Flattening

1.13 ("Update Aquatic", 2018-07-18) is the most structurally invasive release of the modern protocol era, and not primarily because of the gameplay (oceans, conduits, trident, swimming). The protocol-shattering part is The Flattening: Mojang abolished the legacy id:metadata block encoding and the numeric-with-data item encoding that had been the wire format since Beta, replacing it with flat block-state IDs and renumbered item IDs, and made namespaced string IDs (minecraft:stone) the source of truth for blocks, items, entities, sounds, particles, biomes, enchantments, statistics and plugin channels.

Before 1.13, a block on the wire was a 12-bit block id plus a 4-bit metadata nibble (e.g. wool was id 35, colour in the data nibble). After 1.13 every distinct visual/logical state is its own integer in a single flat namespace — roughly 8000+ block states — with no metadata channel at all. The v1_12_2to1_13 mapping table that ViaVersion uses to translate them is sized for 8582 block-state keys (blockconnections/ConnectionData.java:57, KEY_TO_ID = new Object2IntOpenHashMap<>(8582)). Item numeric IDs were likewise renumbered into a new contiguous space (ViaVersion carries an explicit 1.12 → 1.13 item bi-mapping, data/MappingData1_13.java:144-156).

On top of the ID rewrite, 1.13 added four wire-level systems:

1. Declare Commands / Brigadier — server-driven command tree (graph of nodes) replaces the flat string-list tab-complete model. New clientbound Declare Commands packet; tab-complete request/response reworked to be transaction-based.
2. Tags — a new clientbound Tags packet broadcasting block/item/fluid tag groups (#minecraft:logs, #minecraft:wool, …), which commands and recipes reference by tag.
3. Declare Recipes — recipes moved server-side and are pushed to the client as a registry (replaces the recipe-book ID list approach of 1.12).
4. Strict JSON chat + namespaced plugin channels — chat components are now strict JSON, scoreboard objective/team text fields became chat components, and the legacy MC|Brand, MC|StopSound, MC|TrList, … plugin channels were renamed to namespaced minecraft:* channels.

Sources: https://minecraft.wiki/w/Java_Edition_1.13 (fetched 2026-06-19, "added data packs", "added many commands and changed the format of existing commands"); ViaVersion v1_12_2to1_13 (below). The dedicated wiki flattening sub-article (/w/Java_Edition_1.13/flattening) returned 404 on 2026-06-19; the ~8000 block-state figure here is grounded in ViaVersion's 8582-entry map rather than the wiki.

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Protocol changes vs 1.12.2 (393 vs 340), by state

Source: diff of ClientboundPackets1_12_1/ServerboundPackets1_12_1 (used through 1.12.2) against ClientboundPackets1_13/ServerboundPackets1_13 — /tmp/mcproto-refs/ViaVersion/common/src/main/java/com/viaversion/viaversion/protocols/v1_12_2to1_13/packet/; cross-confirmed by minecraft-data packet-name set diff (data/pc/1.12.2 vs data/pc/1.13): +6 clientbound, +10 serverbound net-new play packets, 0 removed.

minecraft-data diff output (play state):

• CB added: declare_commands, tags, declare_recipes, nbt_query_response, face_player, stop_sound
• SB added: query_block_nbt, query_entity_nbt, edit_book, pick_item, name_item, select_trade, set_beacon_effect, update_command_block, update_command_block_minecart, update_structure_block

(stop_sound was a real packet in 1.13; in 1.12.2 it was the MC|StopSound plugin-message, so it shows as "added" in the diff. Likewise several SB additions were previously MC|... plugin messages — see Plugin-channel migration below.)

Handshake / Status / Login

• Status: unchanged on the wire, but the favicon string in the status JSON is now newline-sensitive; ViaVersion strips \n from favicon when downgrading a 1.13 status response (Protocol1_12_2To1_13.java:182-198).
• Login: 1.13 adds Login Plugin Request (CB 0x04) / Login Plugin Response (SB 0x02) — a login-state custom-query channel (this is the mechanism Velocity-modern forwarding later rides on). ViaVersion notes the new CB 0x04 (Protocol1_12_2To1_13.java:201 comment) and cancelServerbound(State.LOGIN, ServerboundLoginPackets.CUSTOM_QUERY_ANSWER.getId()) to drop the SB answer when bridging to a 1.12.2 server (:536).

Play — clientbound, new packets (1.13 = protocol 393)

IDs are the ClientboundPackets1_13 enum ordinals (packet/ClientboundPackets1_13.java):

ID	Enum (ViaVersion)	minecraft-data	Purpose
0x11	COMMANDS	declare_commands	The Brigadier command graph (see Declare Commands below).
0x1D	TAG_QUERY	nbt_query_response	Response to a block/entity NBT query (debug "pick" / data get).
0x31	PLAYER_LOOK_AT	face_player	Server rotates the client to look at a point/entity.
0x4C	STOP_SOUND	stop_sound	Promoted from the old `MC
0x54	UPDATE_RECIPES	declare_recipes	Full recipe registry pushed to the client.
0x55	UPDATE_TAGS	tags	Block/item/fluid tag groups (see Tags below).

The two terminal packets UPDATE_RECIPES (0x54) and UPDATE_TAGS (0x55) are the new high-ID additions; the Declare Commands packet COMMANDS slots in at 0x11, shifting every higher clientbound ID. Note PLACE_GHOST_RECIPE is at 0x2D in 1.13 (ClientboundPackets1_13.java:69).

Beyond the new packets, many existing clientbound packets changed field types because of the Flattening and strict-JSON chat — these don't change the packet set but are heavy translation work:

• BLOCK_UPDATE, MULTI_BLOCK_CHANGE (CHUNK_BLOCKS_UPDATE), LEVEL_CHUNK, BLOCK_EVENT, EXPLODE now carry flat block-state IDs, not id+data (rewriter/WorldPacketRewriter1_13.java).
• SET_OBJECTIVE (0x45) and SET_PLAYER_TEAM (0x47): objective value, team display name, prefix and suffix became chat components (Protocol1_12_2To1_13.java:399-468, ComponentUtil.legacyToJson(...)). Team colour is now an explicit VarInt enum (:441-452).
• MAP_ITEM_DATA icons gained a type field and optional display-name component (:351-371).
• AWARD_STATS statistics are now category-id + registry-id pairs instead of dotted strings (:204-247).

Play — serverbound, new packets (1.13 = protocol 393)

IDs are the ServerboundPackets1_13 enum ordinals (packet/ServerboundPackets1_13.java):

ID	Enum (ViaVersion)	minecraft-data	Was (1.12.2)
0x01	BLOCK_ENTITY_TAG_QUERY	query_block_nbt	new
0x0B	EDIT_BOOK	edit_book	was `MC
0x0C	ENTITY_TAG_QUERY	query_entity_nbt	new
0x15	PICK_ITEM	pick_item	was `MC
0x1C	RENAME_ITEM	name_item	was `MC
0x1F	SELECT_TRADE	select_trade	was `MC
0x20	SET_BEACON	set_beacon_effect	was `MC
0x22	SET_COMMAND_BLOCK	update_command_block	was `MC
0x23	SET_COMMAND_MINECART	update_command_block_minecart	was `MC
0x25	SET_STRUCTURE_BLOCK	update_structure_block	was `MC

This is the other half of the plugin-channel migration: ten interactions that were MC|* custom-payload messages in 1.12.2 became dedicated serverbound packets in 1.13. ViaVersion downgrades each by repackaging it back into the matching legacy MC|* channel — e.g. SET_BEACON → "MC|Beacon" (Protocol1_12_2To1_13.java:657-665), SET_STRUCTURE_BLOCK → "MC|Struct" (:704-762), EDIT_BOOK → "MC|BEdit"/"MC|BSign" (:577-586). The two NBT-query packets (BLOCK_ENTITY_TAG_QUERY 0x01, ENTITY_TAG_QUERY 0x0C) have no 1.12.2 equivalent and are simply cancelled when downgrading (:539, :589).

Data-format changes (no packet add/remove, but wire-breaking)

• Block states: id<<4 | metadata → flat state integer. ViaVersion's WorldPacketRewriter1_13.toNewId(int) is the central mapping call (WorldPacketRewriter1_13.java:566-586).
• Item IDs: renumbered; 1.12 → 1.13 item bi-mapping (MappingData1_13.java:144-156). Spawn eggs collapsed from one item (numeric 383) + entity-id NBT to per-entity flat items (ItemPacketRewriter1_13.java:395-401, :491-493).
• Chat: strict JSON everywhere; legacy §-coded strings in objective/team/score fields must be converted to JSON components (ComponentUtil.legacyToJson, used throughout Protocol1_12_2To1_13.java).
• Plugin channels: legacy MC|Brand, MC|StopSound, MC|TrList, MC|Register/UNREGISTER etc. → namespaced minecraft:*; rename both directions with channel bi-map (ItemPacketRewriter1_13.java:99-169, :199-229; MappingData1_13.java:84-95 loads channelmappings-1.13.json).
• Particles: numeric particle IDs renumbered, several merged/split; ParticleIdMappings1_13.rewriteParticle (WorldPacketRewriter1_13.java:471-537).
• Biomes: invalid biome ids now crash the 1.13 client, so ViaVersion clamps anything outside the valid set to plains (WorldPacketRewriter1_13.java:56-76, :405-421).
• Sounds: named-sound registry renamed/renumbered (NamedSoundMappings1_13, used at WorldPacketRewriter1_13.java:317-327).

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Declare Commands / Brigadier (the command tree)

Before 1.13 the client had no command model: it sent a string to a Tab-Complete packet and the server returned a flat list of completion strings. 1.13 replaces that with a command graph pushed once via the Declare Commands (COMMANDS, CB 0x11) packet, and reworks tab-complete into a transaction-id request/response.

Packet structure (per https://minecraft.wiki/w/Minecraft_Wiki:Projects/wiki.vg_merge/Command_Data, fetched 2026-06-19):

Field	Type	Notes
Count	VarInt	number of nodes in the array
Nodes	Node[]	the graph, flat array; edges are integer indices
Root index	VarInt	index of the (nameless) root node

Each Node:

Field	Type	Present when
Flags	Byte	always
Children count	VarInt	always
Children	VarInt[]	always (indices into the node array)
Redirect node	VarInt	flags & 0x08
Name	String	literal & argument nodes
Parser	(see note)	argument nodes only
Properties	parser-specific	argument nodes only
Suggestions type	Identifier	flags & 0x10

Flags byte: 0x03 = node type (0 root, 1 literal, 2 argument), 0x04 executable, 0x08 has-redirect, 0x10 has-suggestions-type, 0x20 restricted (permission-gated) — wiki, fetched 2026-06-19.

Version-aware note on the Parser field. The merged wiki page describes the modern format where the parser is a VarInt parser-id. In 1.13 specifically the parser is an Identifier (String) such as brigadier:string, and the suggestions type is a String. This is confirmed by ViaVersion writing the parser as Types.STRING, "brigadier:string" and the suggestion provider as Types.STRING, "minecraft:ask_server" in its synthetic command tree (Protocol1_12_2To1_13.java:140, :142). The VarInt parser-id form arrived later (1.19+).

ViaVersion can't synthesise a real 1.12.2 server's command set as a tree, so when bridging a 1.13 client to a 1.12.2 server it sends a minimal fake command graph — a root node plus one greedy brigadier:string argument named args with suggestion provider minecraft:ask_server — so that tab-completion is delegated back to the server (Protocol1_12_2To1_13.java:126-145, SEND_DECLARE_COMMANDS_AND_TAGS). Tab-complete itself becomes transaction-based: the serverbound COMMAND_SUGGESTION carries a transaction id which ViaVersion tracks per-connection (TabCompleteTracker, :542-575), echoing it back on the clientbound COMMAND_SUGGESTIONS (:250-281).

flowchart TD
    R["Root node (flags 0x00, nameless)"] -->|child| L["Literal 'msg'"]
    R -->|child| L2["Literal 'me'"]
    L --> A1["Argument 'target' (parser brigadier:entity)"]
    A1 --> A2["Argument 'message' (parser brigadier:string, executable 0x04)"]
    L2 --> A3["Argument 'action' (parser brigadier:string, executable 0x04)"]
    A2 -.->|redirect 0x08| R

Mermaid is illustrative of the node/edge shape; the literal/argument names are examples, not a captured packet.

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Tags

1.13's Tags packet (UPDATE_TAGS, CB 0x55) ships named groups of registry IDs so the client can resolve #minecraft:logs, #minecraft:wool, fluid tags, etc. for command parsing and rendering. Wire layout (from ViaVersion's emitter, Protocol1_12_2To1_13.java:148-167):

Field	Type	Notes
Block tag count	VarInt
Block tags	(String name, VarInt[] ids)×	each tag = identifier + array of block IDs
Item tag count	VarInt
Item tags	(String, VarInt[])×
Fluid tag count	VarInt
Fluid tags	(String, VarInt[])×

(1.13 has three tag registries — block, item, fluid. Entity-type tags were added in 1.14, and the packet later became a generic per-registry map.) ViaVersion loads the canonical 1.13 tag set from its mapping data (MappingData1_13.loadExtras → loadTags, :62-64) and emits the packet alongside the fake command graph in SEND_DECLARE_COMMANDS_AND_TAGS (:147-173). For 1.20.5+ clients it sends tags in the configuration phase rather than play, because registry data may depend on them (:168-172).

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Per-patch sub-sections

1.13 — protocol 393 (2018-07-18)

The Flattening release; everything above. ViaVersion package: v1_12_2to1_13 — by far the largest single translation package in the codebase (block-connections sub-package, world sub-package, item rewriter, component rewriter, block-entity providers, and an 8582-entry block-state map).

Key commits (git log --oneline -- common/src/main/java/com/viaversion/viaversion/protocols/v1_12_2to1_13):

• e965e9713 — Package/class renames and moves (the package itself)
• 501f65e21 — Packet and entity type renames (Mojang-mapped names)
• 8f8f5e72c — Default rewriter registrations across protocols
• 896c6accf — Fix 1.13 recipe ingredient writing
• 7c80e37e3 — Rewrite item ids in 1.12.2->1.13 show_item hover events (#4671)
• f612adbd0 — Rewrite player & display name in player info packet in 1.12.2->1.13 (#4550)
• 50084c112 — Send the tags packet in 1.12->1.13 before the play login packet (tracking fix)
• 33aecef7b — Handle custom name in block entities in 1.12->1.13 (#4232)
• 80e90a440 — Fix flower pot block storage 1.12.2->1.13 memory leak (#4852)
• cab919bfa — Fix legacy skull rotation overflow in 1.12.2->1.13 (#4952)

1.13.1 — protocol 401 (2018-08-22)

Net packet change: 0 added, 0 removed. A bug-fix patch; the protocol number bumped but no packet was added or deleted. The wire-visible deltas ViaVersion handles in Protocol1_13To1_13_1.java:

1. Command-suggestion slash handling. 1.13.0 had MC-123806 (tab-completion only working on the final argument); the fix changed where the leading / sits. Serverbound COMMAND_SUGGESTION: strip a leading / for compatibility (Protocol1_13To1_13_1.java:61-73). Clientbound COMMAND_SUGGESTIONS: offset the start index by +1 to account for the / (:93-111).
2. Boss bar flags fix (MC-123880). 1.13.0 reused the same byte bit for two different booleans in the Boss Bar packet; 1.13.1 split them. ViaVersion's BOSS_EVENT handler propagates bit 0x02 into bit 0x04 when downgrading (:113-131).
3. Edit Book off-hand fix (MC-84005). EDIT_BOOK now carries a hand VarInt; ViaVersion cancels the packet when hand == 1 (off-hand) since 1.13.0 servers don't expect it (:75-91).
4. Item-registry tag rewrite registered (tagRewriter.register(... UPDATE_TAGS, RegistryType.ITEM), :133) — reflects minor item-tag additions in 1.13.1.

(Wiki notes the non-protocol changes too: %= scoreboard operator switched to Math.floorMod, function error line numbers start at 1 — https://minecraft.wiki/w/Java_Edition_1.13.1, fetched 2026-06-19.)

ViaVersion package: v1_13to1_13_1 (note its MappingDataBase("1.13", "1.13.2") — it shares mapping data with the 1.13.2 step, Protocol1_13To1_13_1.java:44). Key commits (git log -- …/v1_13to1_13_1): e965e9713 (package creation), 501f65e21 (packet/entity renames), c13b40a37 (Add ParticleRewriter base), bb48dc90f (registerBlockStateHandler).

1.13.2 — protocol 404 (2018-10-22)

Net packet change: 0 added, 0 removed. One data-format change: the Slot format. This is the only wire-visible change, and it is a clean before/after:

	1.13 / 1.13.1 (ItemType1_13)	1.13.2 (ItemType1_13_2)
Empty marker	Short id = -1	Boolean present = false
Item id	Short	VarInt
Then	Byte count, NBT	Byte count, NBT

So 1.13.2 (a) replaced the "id = −1 means empty" sentinel with an explicit leading present boolean, and (b) widened the item id from a Short to a VarInt. Confirmed by the two type classes: ItemType1_13.read reads short id; if (id < 0) return null (api/.../type/types/item/ItemType1_13.java:38-46) vs ItemType1_13_2.read reads boolean present; if (!present) return null; … VAR_INT id (api/.../type/types/item/ItemType1_13_2.java:38-46).

ViaVersion's v1_13_1to1_13_2 package therefore does almost nothing except retype every Slot field on every item-bearing packet from ITEM1_13 ↔ ITEM1_13_2:

• CONTAINER_SET_SLOT, CONTAINER_SET_CONTENT, SET_EQUIPPED_ITEM, UPDATE_RECIPES, the minecraft:trader_list plugin payload — all map(Types.ITEM1_13, Types.ITEM1_13_2) clientbound (rewriter/ItemPacketRewriter1_13_2.java:30-114).
• CONTAINER_CLICK, SET_CREATIVE_MODE_SLOT, EDIT_BOOK — map(Types.ITEM1_13_2, Types.ITEM1_13) serverbound (:116-133; Protocol1_13_1To1_13_2.java:42-47).
• UPDATE_ADVANCEMENTS icon retyped ITEM1_13 → ITEM1_13_2 (Protocol1_13_1To1_13_2.java:49-79).
• One area-effect-cloud item-particle fix (commit ee16d7af2).

ViaVersion package: v1_13_1to1_13_2. Key commits (git log -- …/v1_13_1to1_13_2): e965e9713 (package creation), 501f65e21 (renames), ee16d7af2 (Fix two area effect cloud item particle issues), 5286efde1 (move type instances out of enclosing class).

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Proxy and translation impact

Why v1_12_2to1_13 is ViaVersion's largest translation class

The 1.12.2→1.13 step is the heaviest in ViaVersion for three compounding reasons, all stemming from the Flattening:

1. The ~8000-entry block-state remap. Every block on every chunk, block-update, multi-block-change, block-event and explode packet must be rewritten from legacy id<<4|data to a flat 1.13 state. The mapping table is sized for 8582 entries (blockconnections/ConnectionData.java:57). The chunk path rewrites every palette entry in every section via toNewId (WorldPacketRewriter1_13.java:338-347, :566-586).

2. Block connections must be computed proxy-side. Pre-1.13, the appearance of fences, walls, glass panes, stairs, redstone, doors, chests, tripwire, vines, chorus plants, fire, stems, etc. was derived client-side from neighbours; 1.13 bakes the connected variant into the block state, so a 1.13 client expects the server to have already chosen oak_fence[north=true,east=true,...]. A 1.12.2 server doesn't send that, so ViaVersion runs a full server-side block-connection engine: it stores chunk block data (storage/BlockStorage.java, BlockConnectionStorage), and on every chunk load / block change recomputes neighbour connections with 19 dedicated connection-handler classes (blockconnections/*ConnectionHandler.java — Wall, Stair, Door, Chest, Fence, NetherFence, Glass, Pane, Redstone, Tripwire, Vine, ChorusPlant, Fire, Pumpkin, Melon, Snowy-grass, Flower, Stem, …). This is unique to this version step — no other ViaVersion package carries a world-geometry simulator. Gated behind serverside-block-connections config.

3. Everything else got renumbered or restructured at once. Item bi-map, spawn-egg split, particle remap, named-sound remap, biome clamp, statistics restructure, chat→JSON on scoreboard/team fields, plugin-channel namespacing in both directions, plus block-entity→block synthesis (note blocks and flower pots stopped being block-entities and became states, so ViaVersion deletes their NBT block-entities and bakes the state in, WorldPacketRewriter1_13.java:423-452). The package therefore needs sub-packages blockconnections/, data/, provider/blockentities/, rewriter/, storage/, task/ — the only version step that needs all of them.

What a proxy must do for a 1.13 client → 1.12.2 server

• Translate every block state down (flat → id+data) on all world packets, and strip connection bits that the old server never set.
• Synthesise a fake Declare Commands graph + Tags packet at join (so command UI and tag-referencing recipes don't break) — SEND_DECLARE_COMMANDS_AND_TAGS.
• Repackage the 10 new serverbound packets back into their legacy MC|* plugin messages; cancel the two NBT-query packets.
• Down-convert chat JSON on objective/team/score fields to legacy § strings; rename plugin channels minecraft:* → MC|*.
• Map items down (incl. spawn eggs, show_item hover events), remap particles/sounds, clamp biomes to avoid client crashes.

Going the other way / between patches

• A 1.13.1 server vs 1.13.0 client (or vice-versa): only the command-suggestion / offset, boss-bar flag split, and edit-book hand need handling — trivial next to the 1.13 step.
• A 1.13.2 server vs 1.13/1.13.1 client: only the Slot format (present boolean + VarInt id ↔ Short-sentinel) needs retyping on item-bearing packets. A proxy that gets this wrong corrupts every inventory and creative action.

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Why this version matters as a baseline

1.13.2 (protocol 404) is the stable terminal of the Flattening line and a common multi-version proxy target: it is the last point before 1.14's further entity/tag/registry churn, and the first protocol where blocks, items, commands, tags and recipes all use the modern flat/namespaced model. Everything from 1.14 onward builds on the 1.13 data model rather than re-inventing it; the next equally-invasive jump is 1.20.2's Configuration state, not a data re-flattening.