> ## Documentation Index > Fetch the complete documentation index at: https://docs.kuru.io/llms.txt > Use this file to discover all available pages before exploring further. # L2 book stream > Receive complete finalized order-book snapshots on a fixed cadence. ```text theme={null} l2Book@f@ ``` This market-scoped snapshot stream sends the current finalized book when the subscription starts and then publishes complete snapshots on the requested cadence. It does not use a replay cursor. ## Subscribe ```json theme={null} { "op": "sub", "id": 3, "t": "l2Book@f@500", "m": "0x8121EE960066e4344A213F9aC7502395502aEe7a", "feedEpoch": 0, "n": 20, "g": "sf", "sf": 5, "mt": 2, "e": false } ``` `n` is depth per side from `1` through `200`. Grouping `g` is `none`, `tick`, or `sf`. Use `tk` with tick grouping, `sf` and optional `mt` with significant figures, and `e=true` for active/passive decomposition. ## Decoded event The shape below is the inner `message` returned by `decodeExchangeWsEnvelope` or `decodeExchangeWsMessage`. Every binary socket message also carries an outer `id: bigint`, matching your subscription ID. Use it to route snapshots, replay, and live updates. See [binary subscription envelopes](/api/exchange/websocket#binary-subscription-envelope). ```ts theme={null} type ExchangeWsL2Grouping = | { kind: "none" } | { kind: "nativeTick"; tickSize: bigint } | { kind: "significantFigures"; figures: number; mantissa: number | null; }; interface ExchangeWsCompactL2Level { price: bigint; totalBase: bigint; } interface ExchangeWsExtendedL2Level extends ExchangeWsCompactL2Level { activeBase: bigint; passiveBase: bigint; activeOrderCount: number; } interface ExchangeWsL2BookFrameBase { wireVersion: 1; feedEpoch: bigint; view: "finalized"; kind: "l2Book"; marketAddress: string; marketSeq: bigint; globalSeq: bigint; stateHead: { blockNumber: bigint; blockId: string }; durationMs: bigint; maxDepthPerSide: number; grouping: ExchangeWsL2Grouping; } type ExchangeWsL2BookFrame = | (ExchangeWsL2BookFrameBase & { levelFormat: "compact"; bids: ExchangeWsCompactL2Level[]; asks: ExchangeWsCompactL2Level[]; }) | (ExchangeWsL2BookFrameBase & { levelFormat: "extended"; bids: ExchangeWsExtendedL2Level[]; asks: ExchangeWsExtendedL2Level[]; }); ``` Bids are ordered high to low and asks low to high. Prices are native pp integers; base quantities remain native integers in market size precision. The decoder performs no scaling. Native tick grouping keeps `tickSize` in protocol ticks. ## AsyncAPI ````yaml api/exchange/asyncapi.yaml l2Book id: l2Book title: Subscribe to L2 book snapshots description: Receive complete finalized order-book snapshots on a fixed cadence. servers: - id: mainnet protocol: wss host: gateway.mainnet.kuru.io bindings: [] variables: [] - id: testnet protocol: wss host: gateway.testnet.kuru.io bindings: [] variables: [] address: /ws parameters: [] bindings: [] operations: - &ref_1 id: subscribeL2Book title: Subscribe l2 book type: receive messages: - &ref_2 id: request contentType: application/json payload: - name: l2Book@f subscription type: object properties: - name: op type: string enumValues: - sub required: true - name: id type: integer description: >- JSON integer restricted to JavaScript's exact safe-integer range. required: true - name: t type: string required: true - name: m type: string description: Lowercase 20-byte market contract address. required: true - name: feedEpoch type: integer description: Feed namespace. Required when seq is supplied. required: false - name: 'n' type: integer required: false - name: g type: string enumValues: - none - tick - sf required: false - name: tk type: integer required: false - name: sf type: integer description: Required with g=sf. Values outside 2 through 5 are rejected. required: false - name: mt type: integer description: Optional mantissa bucket. Valid only when g=sf and sf=5. enumValues: - 1 - 2 - 5 required: false - name: e type: boolean required: false headers: [] jsonPayloadSchema: type: object additionalProperties: false required: - op - id - t - m allOf: - if: properties: g: const: tick required: - g x-parser-schema-id: then: required: - tk not: anyOf: - required: - sf x-parser-schema-id: - required: - mt x-parser-schema-id: x-parser-schema-id: x-parser-schema-id: x-parser-schema-id: - if: properties: g: const: sf required: - g x-parser-schema-id: then: required: - sf not: required: - tk x-parser-schema-id: x-parser-schema-id: x-parser-schema-id: - if: properties: g: const: sf sf: const: 5 required: - g - sf x-parser-schema-id: else: not: required: - mt x-parser-schema-id: x-parser-schema-id: x-parser-schema-id: - if: anyOf: - properties: g: const: none required: - g x-parser-schema-id: - not: required: - g x-parser-schema-id: x-parser-schema-id: x-parser-schema-id: then: not: anyOf: - required: - tk x-parser-schema-id: - required: - sf x-parser-schema-id: - required: - mt x-parser-schema-id: x-parser-schema-id: x-parser-schema-id: x-parser-schema-id: properties: op: type: string enum: - sub x-parser-schema-id: id: &ref_0 type: integer minimum: 0 maximum: 9007199254740991 description: >- JSON integer restricted to JavaScript's exact safe-integer range. x-parser-schema-id: ControlInteger t: type: string pattern: ^l2Book@f@[1-9][0-9]*$ x-parser-schema-id: m: type: string pattern: ^0x[0-9a-f]{40}$ description: Lowercase 20-byte market contract address. x-parser-schema-id: MarketAddress feedEpoch: allOf: - *ref_0 description: Feed namespace. Required when seq is supplied. x-parser-schema-id: FeedEpoch 'n': type: integer minimum: 1 maximum: 200 default: 20 x-parser-schema-id: g: type: string enum: - none - tick - sf default: none x-parser-schema-id: tk: allOf: - *ref_0 - minimum: 1 x-parser-schema-id: x-parser-schema-id: sf: type: integer minimum: 2 maximum: 5 description: Required with g=sf. Values outside 2 through 5 are rejected. x-parser-schema-id: mt: type: integer enum: - 1 - 2 - 5 description: Optional mantissa bucket. Valid only when g=sf and sf=5. x-parser-schema-id: e: type: boolean default: false x-parser-schema-id: x-parser-schema-id: L2BookSubscription title: l2Book@f subscription example: |- { "op": "sub", "id": 3, "t": "l2Book@f@500", "m": "0x8121EE960066e4344A213F9aC7502395502aEe7a", "feedEpoch": 0, "n": 20, "g": "sf", "sf": 5, "mt": 2, "e": false } bindings: [] extensions: - id: x-parser-unique-object-id value: request bindings: [] extensions: - id: x-parser-unique-object-id value: l2Book sendOperations: - *ref_1 receiveOperations: [] sendMessages: - *ref_2 receiveMessages: [] extensions: - id: x-parser-unique-object-id value: l2Book securitySchemes: [] ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.