Polymarket WebSocket API: Streaming Real-Time Order Book Data
If your bot polls REST endpoints for prices, it is always a step behind. The WebSocket API pushes order-book and trade updates the instant they happen — the foundation of any fast, reliable Polymarket bot.
Why real-time data matters
Strategies like arbitrage, market making, and news trading depend on acting before the market moves. A polled snapshot is stale by the time you read it; a stream keeps your view of the book current.
WebSocket vs REST polling
| WebSocket | REST polling | |
|---|---|---|
| Freshness | Pushed instantly | As stale as your interval |
| Request load | One connection | Many repeated calls |
| Rate-limit risk | Low | High |
| Best for | Live data | One-off actions |
In short: stream data, and use REST for actions like placing and cancelling orders. This also keeps you well clear of rate limits.
Available channels
- Market / book channel: live order-book and price updates.
- Trade channel: executions as they happen.
- User channel: updates on your own orders and fills.
Subscribing and parsing
After opening the connection, send a subscription message listing the channels and market token IDs you care about. Then handle incoming messages in an event loop, updating your local state on each one.
# Pseudocode
ws = connect("wss://ws-subscriptions-clob.polymarket.com/...")
ws.send(subscribe(channel="market", assets=[TOKEN_ID]))
for msg in ws:
update_local_book(parse(msg))Handling disconnects and resyncing
Connections drop. If you do not detect and recover, your bot trades on a frozen book — one of the most dangerous silent failures. Always implement heartbeat checks, automatic reconnection, and a full state resync after reconnecting.
Building a reliable local book
- Load an initial snapshot of the book.
- Apply streamed updates in order to keep it current.
- On disconnect, discard the stale book and resync from a fresh snapshot.
- Sanity-check the book (e.g. best bid < best ask) before trading on it.
PolyBot maintains a reconnect-safe live order book from the WebSocket feed, so its strategies always act on current data rather than a stale snapshot.
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Frequently Asked Questions
Disclaimer: This article is for educational purposes only and is not financial, investment, or legal advice. Prediction-market trading carries a real risk of loss. Automation does not guarantee profit, and past performance never guarantees future results. Only trade funds you can afford to lose, and confirm that Polymarket is available and legal in your jurisdiction before trading.