> ## Documentation Index > Fetch the complete documentation index at: https://docs.arcus.xyz/llms.txt > Use this file to discover all available pages before exploring further. # Bbo > > **Endpoint:** `wss://api.testnet.arcus.xyz/v1/ws` — one socket multiplexes every channel and RPC request. Click **Connect**, then send the example subscribe message below to start receiving data. Best bid and offer (top-of-book) for a single market. Lower bandwidth than `l2Orderbook` when only the inside quote is needed. ## AsyncAPI ````yaml api-reference/asyncapi.yaml bbo id: bbo title: Bbo description: > > **Endpoint:** `wss://api.testnet.arcus.xyz/v1/ws` — one socket multiplexes every channel and RPC request. Click **Connect**, then send the example subscribe message below to start receiving data. Best bid and offer (top-of-book) for a single market. Lower bandwidth than `l2Orderbook` when only the inside quote is needed. servers: - id: testnet protocol: wss host: api.testnet.arcus.xyz bindings: [] variables: [] - id: mainnet protocol: wss host: api.arcus.xyz bindings: [] variables: [] address: /v1/ws?channel=bbo parameters: [] bindings: [] operations: - &ref_2 id: subscribeBBO title: Subscribe b b o type: receive messages: - &ref_4 id: subscribe contentType: application/json payload: - name: Subscribe to a market channel type: object properties: - name: type type: string description: subscribe required: true - name: channel type: string enumValues: - trades - oraclePrices - bbo required: true - name: id type: string description: Market display name (e.g. "BTC-USD"). required: true headers: [] jsonPayloadSchema: type: object required: - type - channel - id properties: type: type: string const: subscribe x-parser-schema-id: channel: type: string enum: - trades - oraclePrices - bbo x-parser-schema-id: id: type: string description: Market display name (e.g. "BTC-USD"). example: BTC-USD x-parser-schema-id: x-parser-schema-id: SubscribeByMarketPayload title: Subscribe to a market channel example: |- { "type": "subscribe", "channel": "trades", "id": "BTC-USD" } bindings: [] extensions: - id: x-parser-unique-object-id value: subscribe bindings: [] extensions: &ref_1 - id: x-parser-unique-object-id value: bbo - &ref_3 id: receiveBBO title: Receive b b o type: send messages: - &ref_5 id: update contentType: application/json payload: - allOf: &ref_0 - type: object description: Common envelope for all server-pushed channel messages. required: - type - channel properties: type: type: string enum: - subscribed - channel_data description: >- `subscribed` for the initial snapshot; `channel_data` for updates. x-parser-schema-id: channel: type: string description: Channel name. x-parser-schema-id: id: type: string description: >- Channel id (market or address). Absent for global channels. x-parser-schema-id: contents: type: object additionalProperties: true description: Channel-specific payload. Schema varies by channel. properties: {} x-parser-schema-id: x-parser-schema-id: ChannelDataEnvelope - type: object properties: type: const: channel_data x-parser-schema-id: contents: type: object required: - bestBid - bestAsk - timestamp - lastSequenceId - globalSequenceId properties: bestBid: type: object nullable: true description: Best bid level, or null when the bid side is empty. required: - price - size properties: price: type: string example: '94500.00' x-parser-schema-id: size: type: string example: '1.5' x-parser-schema-id: x-parser-schema-id: bestAsk: type: object nullable: true description: Best ask level, or null when the ask side is empty. required: - price - size properties: price: type: string example: '94501.00' x-parser-schema-id: size: type: string example: '0.8' x-parser-schema-id: x-parser-schema-id: timestamp: type: integer format: int64 description: Unix microseconds when the top-of-book was stamped. example: 1780410803123456 x-parser-schema-id: lastSequenceId: type: integer description: Per-market orderbook sequence for this BBO frame. example: 2001 x-parser-schema-id: globalSequenceId: type: integer description: Cross-market monotonic sequence. example: 880422 x-parser-schema-id: x-parser-schema-id: x-parser-schema-id: x-parser-schema-id: BBOUpdatePayload name: Best Bid Offer (BBO) Update headers: [] jsonPayloadSchema: allOf: *ref_0 x-parser-schema-id: BBOUpdatePayload title: Best Bid Offer (BBO) Update example: |- { "type": "channel_data", "channel": "bbo", "id": "BTC-USD", "contents": { "bestBid": { "price": "94500.00", "size": "1.5" }, "bestAsk": { "price": "94501.00", "size": "0.8" }, "timestamp": 1780410803123456, "lastSequenceId": 2001, "globalSequenceId": 880422 } } bindings: [] extensions: - id: x-parser-unique-object-id value: update bindings: [] extensions: *ref_1 sendOperations: - *ref_2 receiveOperations: - *ref_3 sendMessages: - *ref_4 receiveMessages: - *ref_5 extensions: - id: x-parser-unique-object-id value: bbo securitySchemes: [] ````