Messages

{
  "type": "subscribed",
  "channel": "l2Orderbook",
  "id": "BTC-USD",
  "contents": {
    "bids": [
      [
        "94500.0",
        "1.5"
      ],
      [
        "94499.0",
        "2.0"
      ]
    ],
    "asks": [
      [
        "94501.0",
        "0.8"
      ],
      [
        "94502.0",
        "3.1"
      ]
    ],
    "lastSequenceId": 1042,
    "globalSequenceId": 880421,
    "timestamp": 1780410803123456
  }
}

{
  "type": "channel_data",
  "channel": "l2OrderbookUpdates",
  "id": "BTC-USD",
  "contents": {
    "bids": [
      [
        "94499.0",
        "0"
      ]
    ],
    "asks": [
      [
        "94503.0",
        "1.2"
      ]
    ],
    "lastSequenceId": 1043,
    "globalSequenceId": 880422
  }
}

Market data

L2 orderbook updates

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.

Full L2 orderbook snapshot followed by event-driven incremental deltas for a single market.

On subscribe: full snapshot up to nLevels per side, then delta updates as orders are placed, modified, or cancelled. Each delta carries a monotonically increasing lastSequenceId (continuous with the snapshot’s lastSequenceId) — drop or re-subscribe on any gap.

WSS

ws?channel=l2OrderbookUpdates

Messages

{
  "type": "subscribed",
  "channel": "l2Orderbook",
  "id": "BTC-USD",
  "contents": {
    "bids": [
      [
        "94500.0",
        "1.5"
      ],
      [
        "94499.0",
        "2.0"
      ]
    ],
    "asks": [
      [
        "94501.0",
        "0.8"
      ],
      [
        "94502.0",
        "3.1"
      ]
    ],
    "lastSequenceId": 1042,
    "globalSequenceId": 880421,
    "timestamp": 1780410803123456
  }
}

{
  "type": "channel_data",
  "channel": "l2OrderbookUpdates",
  "id": "BTC-USD",
  "contents": {
    "bids": [
      [
        "94499.0",
        "0"
      ]
    ],
    "asks": [
      [
        "94503.0",
        "1.2"
      ]
    ],
    "lastSequenceId": 1043,
    "globalSequenceId": 880422
  }
}

Subscribe to L2 Orderbook incremental updates

type:object

L2 Orderbook Snapshot

L2 Orderbook Incremental Update

size: "0" means the level was removed. Drop or re-subscribe on any lastSequenceId gap.

L2 orderbook Trades