> ## Documentation Index
> Fetch the complete documentation index at: https://docs.novig.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Order Book Channel

> Subscribe to real-time order book updates

## Order Book Channel

Subscribe to public order book updates including order placements and cancellations.

### Channel Names

* **Global tape:** `tape` - Receive updates for all markets
* **Market-specific:** `{marketId}` - Receive updates only for a specific market (UUID)

<Note>
  When subscribing to a **specific market**, you will receive initial `book` messages containing the current order book state. When subscribing to the **global tape** (`tape`), you will **not** receive these initial order book state messages—only subsequent updates.
</Note>

### Subscription

<CodeGroup>
  ```javascript Global Tape theme={null}
  // Subscribe to all markets
  ws.send(JSON.stringify({
    event: 'subscribe',
    data: 'tape'
  }));
  ```

  ```javascript Specific Market theme={null}
  // Subscribe to a specific market
  ws.send(JSON.stringify({
    event: 'subscribe',
    data: '123e4567-e89b-12d3-a456-426614174000' // Market ID
  }));
  ```
</CodeGroup>

### Event Types

The order book channel broadcasts two types of events:

* **PLACE** - A new order has been placed or an existing order has been partially filled
* **CANCEL** - An order has been explicitly cancelled

<Note>
  Implicit cancellations (e.g., when a market closes) are **not** broadcast on this channel. Use the [Market Lifecycle Channel](/api-reference/WSS/lifecycle-channel) to handle those events.
</Note>

### Message Format

```json theme={null}
{
  "event": "book",
  "data": {
    "type": "PLACE",
    "order": {
      "price": 0.667,
      "qty": 110,
      "originalQty": 110,
      "outcomeId": "123e4567-e89b-12d3-a456-426614174000"
    },
    "fills": [
      {
        "id": "fill-123",
        "orderId": "order-456",
        "price": 0.667,
        "qty": 50,
        "isWash": false,
        "isTaker": true,
        "marketId": "market-789",
        "outcomeId": "123e4567-e89b-12d3-a456-426614174000"
      }
    ],
    "market": {
      "id": "market-789",
      "description": "KC v BUF Total",
      "status": "OPEN",
      "type": "TOTAL",
      "strike": 26.5,
      "volume": 1000000
    }
  }
}
```

### Order Fields

| Field         | Type   | Description                                                                 |
| ------------- | ------ | --------------------------------------------------------------------------- |
| `price`       | number | The price of the order in decimal probability (0-1, up to 3 decimal places) |
| `qty`         | number | The remaining quantity in Minimum Currency Units                            |
| `originalQty` | number | The original quantity when the order was placed                             |
| `outcomeId`   | string | UUID of the outcome for this order                                          |

### Fill Fields

| Field       | Type    | Description                                |
| ----------- | ------- | ------------------------------------------ |
| `id`        | string  | UUID of the fill                           |
| `orderId`   | string  | UUID of the order that was filled          |
| `price`     | number  | The execution price in decimal probability |
| `qty`       | number  | The quantity filled                        |
| `isWash`    | boolean | Whether this is a wash trade               |
| `isTaker`   | boolean | Whether this fill was the taker side       |
| `marketId`  | string  | UUID of the market                         |
| `outcomeId` | string  | UUID of the outcome                        |

### Example Implementation

<CodeGroup>
  ```javascript JavaScript/TypeScript theme={null}
  import WebSocket from 'ws';

  const ws = new WebSocket('wss://api.novig.us/tape', {
    headers: {
      'Authorization': `Bearer ${ACCESS_TOKEN}`
    }
  });

  ws.on('open', () => {
    // Subscribe to global tape
    ws.send(JSON.stringify({
      event: 'subscribe',
      data: 'tape'
    }));
  });

  ws.on('message', (data) => {
    const message = JSON.parse(data.toString());

    if (message.event === 'book') {
      const { type, order, fills, market } = message.data;

      console.log(`${type} event for market: ${market.description}`);
      console.log(`Order: ${order.qty} @ ${order.price}`);

      if (fills.length > 0) {
        console.log(`Fills: ${fills.length}`);
        fills.forEach(fill => {
          console.log(`  - ${fill.qty} @ ${fill.price}`);
        });
      }
    }
  });
  ```
</CodeGroup>

### Unsubscribing

To stop receiving updates from a channel:

```javascript theme={null}
ws.send(JSON.stringify({
  event: 'unsubscribe',
  data: 'tape'
}));
```

You'll receive a confirmation:

```json theme={null}
{
  "event": "unsubscribed",
  "data": {
    "channel": "tape"
  }
}
```