> For the complete documentation index, see [llms.txt](https://dev.strixlab.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://dev.strixlab.io/typescript-sdk/orderbook.md).

# Order Book

Every read on this page is **public**. For a continuously updating book, subscribe over [WebSocket](/typescript-sdk/websockets.md) instead of polling these.

### Snapshot

```ts
const book = await client.orderbook.snapshot(tokenId, { depth: 20 });

book.bids;   // [{ price: 0.62, size: 500 }, { price: 0.61, size: 300 }, …] highest first
book.asks;   // [{ price: 0.63, size: 200 }, { price: 0.64, size: 450 }, …] lowest first
```

`depth` is levels per side — default 50, maximum 200. `size` is the total shares resting at that price.

{% code title="Printing a book" %}

```ts
const book = await client.orderbook.snapshot(tokenId, { depth: 5 });

console.log('    price    size');
for (const a of [...book.asks].reverse()) console.log(`ASK ${a.price.toFixed(3)}  ${a.size}`);
console.log('    ────────────');
for (const b of book.bids)                console.log(`BID ${b.price.toFixed(3)}  ${b.size}`);
```

{% endcode %}

### Midpoint

```ts
const { mid } = await client.orderbook.midpoint(tokenId);   // (bestBid + bestAsk) / 2
```

{% hint style="warning" %}
`midpoint()` throws a `StrixApiError` with `status: 404` when either side of the book is empty — a one-sided book has no midpoint to report. Catch it, or read `client.ws.orderbook.getMid(tokenId)` instead, which returns `null` fields rather than throwing.
{% endhint %}

### Best price

```ts
const { price: bestAsk } = await client.orderbook.price(tokenId, 'buy');   // lowest you can buy at
const { price: bestBid } = await client.orderbook.price(tokenId, 'sell');  // highest you can sell at
```

The side names the action you want to take, not the book side: `'buy'` returns the best **ask**, `'sell'` the best **bid**.

### Reading both sides from one book

YES and NO are complements — a bid on YES at `P` is an ask on NO at `1 − P` — so one subscription gives you both. The SDK computes it for you:

```ts
client.ws.orderbook.subscribe([yesTokenId], {
  onMid: ({ yesMid, noMid, bestBid, bestAsk }) => {
    console.log(`YES ${yesMid} (${bestBid}/${bestAsk})  ·  NO ${noMid}`);
  },
});
```

{% hint style="info" %}
The venue's own price ladder subscribes to **both** tokenIds and mirrors each into the other, so a user's NO orders show on the YES ladder. If you're rendering a book, do the same: subscribe to both legs and merge, rather than assuming one book carries everything.
{% endhint %}

### Snapshot or stream?

<table><thead><tr><th width="230">Use</th><th>When</th></tr></thead><tbody><tr><td><code>orderbook.snapshot()</code></td><td>One-off reads, backtests, health checks, and re-syncing after a gap.</td></tr><tr><td><code>ws.orderbook.subscribe()</code></td><td>Anything live. The server sends one snapshot then incremental deltas; the SDK merges them and hands you a maintained book.</td></tr><tr><td><code>ws.orderbook.getBook()</code></td><td>Synchronous read of the SDK's cached book, with no request at all — the right call inside a quoting loop.</td></tr></tbody></table>

{% hint style="danger" %}
**Don't poll `snapshot()` in a loop.** Read endpoints are rate limited, and a poll interval that keeps up with the book will burn your budget for no benefit. One WebSocket subscription costs nothing per update.
{% endhint %}


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