--- url: "https://predictiontoolkit.com/tools/polymarket-clob-api/" publisher: "PredictionToolkit" dateModified: "2026-11-03" --- [← Data APIs]() ![Polymarket CLOB API logo]() Data API # Polymarket CLOB API: read books and implement order handling The Polymarket CLOB API exposes public prices and outcome-token books alongside authenticated order placement, cancellation and management. Gamma discovery supplies the market and outcome IDs needed to start. [**4.0**/ 5Editorial rating]() [Editorial assessment]() [Read CLOB price and book documentation]() docs.polymarket.com **Available on:** API **Pricing:** [See plans and costs ↓]() [Screenshots]() [Explore alternatives]() [Data APIs]() [Official developer tools]() ## Screenshots and interface Product preview1 / 2 Provider documentation for public market-data queries. ## What is Polymarket CLOB API? Use bids and asks from the public book to show price levels alongside their trading constraints. Midpoint, spread and last-trade data come from reference endpoints; check the price side and outcome identifiers before putting the snapshot in an interface or execution service. A source-recorded unauthenticated CTF book check returned identifiers matching the selected Gamma outcome. That is narrower than testing private access: signing, submission, cancellation, fills and sustained latency were not exercised. API credentials and wallet order authorization remain separate implementation requirements. ### Who it is for - Building trading interfaces or execution services. - Researching spread and book depth. - Implementing signing and transport under direct application control. ## Data and API methods - **Outcome books** Read bids, asks, tick size, minimum order size, state hash and market identifiers. - **Price sides** BUY returns the best ask; SELL returns the best bid. - **Reference values** Retrieve midpoint, spread and last traded price separately. - **Batch requests** Supported book and price requests accept up to 500 items. - **Order handling** Use the authenticated surface for signed submission, cancellation and order management. - **Authentication layers** L1 wallet signing creates or derives credentials; L2 signs private requests, while a separate wallet signature authorizes the order. - **Observed identifier mapping** The public sample returned market, asset\_id, timestamp, bids and asks. market matched Gamma conditionId and asset\_id matched the requested outcome token. ## Integration tasks ### Display an executable-price view Find token IDs through Gamma, read the book and show best bid, ask and depth. Label midpoint separately from prices available on the book. ### Build an order service Create or derive API credentials, implement exact request signing and track submitted order state. Add cancellation and reconciliation before automating order generation; a separate wallet signature must authorize the order. ### Validate the handoff For the returned book, match asset\_id to the selected outcome token and market to Gamma's conditionId before using bids or asks. Keep the snapshot timestamp with the levels: a successful read does not establish that an order would fill at the quoted price. ## Pricing and total cost Public market reads do not require credentials. The integration guide lists no separate API subscription; venue fees apply to eligible trades. ## API access and setup 1. Discover the market and labeled outcome-token IDs through Gamma. 2. Request the labeled outcome's public book or price. For a book response, match asset\_id to its outcome token and market to the condition before using the levels. 3. Respect tick size and minimum order size. 4. For private operations, configure wallet signing and L2 credentials. 5. Keep serialized request bodies exactly consistent with their signatures. [CLOB API base endpoint]() ## Useful links - [Polymarket Discord community]() ### What to check - The documentation describes best bid/ask levels at the end of book arrays. - Midpoint is not necessarily executable. - A never-traded token can return null for last trade. - Gamma market id, conditionId and outcome token ID are different identifiers. - Only a public snapshot was checked; private orders, fills and sustained latency were not tested. ## Public book observations One unauthenticated CTF order book was read using an outcome token selected from Gamma. ### Join the book to the selected outcome Action completedObserved on 2026-11-03T12:52:24.370757+00:00 **Action:** Requested /book with the selected token\_id and compared the response identifiers with Gamma. **Result:** HTTP 200 returned asset\_id matching that token and market matching its conditionId. The response included bids, asks, timestamp, tick\_size and min\_order\_size. **Scope and limits:** One public book was checked. No wallet, signing, order submission, cancellation or fill was exercised. [Checked source]() ### Inspect ordering and numeric fields Action completedObserved on 2026-11-03T12:52:24.370757+00:00 **Action:** Counted levels and examined price, size and trading constraints in the saved book response. **Result:** The snapshot contained 20 bid levels and 139 ask levels. Bids increased and asks decreased through their arrays, placing each best price last. Price and size were decimal strings; tick\_size was 0.001 and min\_order\_size was 5. **Scope and limits:** These are dated snapshot values for this book, not universal market settings or measured execution latency. Resting size can change before an order. [Checked source]() The book answers what was quoted for one outcome at that moment. Gamma's market metadata and Data API's activity totals answer different questions; neither a last-trade number nor an aggregate total substitutes for that outcome's depth snapshot. A closer look ## Ratings & reviews Editorial rating **4.0**/ 5 0 user reviews PredictionToolkit editorial ### Our take on Polymarket CLOB API CLOB suits integrations that need direct book access and explicit control over authentication. Mapping identifiers, choosing the price side and following order conventions are the main implementation responsibilities. **Assessment criteria:** Task usefulness, documented scope, setup clarity, and access and cost transparency. **Assessment date:** 2026-10-01 **Documentation reviewed:** 2026-10-01 Documentation-based assessment. [How we rate]() ### User reviews 0 The main score switches to user ratings after 5 published reviews. **Be the first to share your experience** A specific example helps the next person choose the right tool. ## Related tools [Browse category]() ![Official @polymarket/client TypeScript quickstart]() ![@polymarket/client logo]()[@polymarket/client]() SDK**4.0**Editorial Build typed Polymarket apps with public reads, resumable scans, real-time topics and separate authenticated actions. - Language TypeScript · JavaScript Use the official typed TypeScript client. ![Official Polymarket public analytics integration guide]() ![Polymarket Data API logo]()[Polymarket Data API]() Data API**4.0**Editorial Retrieve positions, trades, holders and rankings while preserving outcome IDs and pagination context. - Access API Query positions and public account activity. ![Official Polymarket Gamma API market-discovery documentation]() ![Polymarket Gamma API logo]()[Polymarket Gamma API]() Data API**4.0**Editorial Discover contracts and their identifiers before querying executable prices or building a searchable catalog. - Access API Discover events, markets and outcome tokens. ## Guides and workflows - [Polymarket API key and authentication]() - [Polymarket API endpoints: Gamma, CLOB and Data]() - [What is Polymarket?]() ## Frequently asked questions about Polymarket CLOB API ### Do public price reads need a wallet? No. Public market reads require no credentials. ### Where do I find token IDs? Use Gamma discovery and market metadata. ### Is midpoint the buy price? No. Buying uses the ask; midpoint averages best bid and ask. ### Why use API and wallet signatures? L2 authenticates the request; the wallet signature authorizes the order. ### Should book.market equal Gamma id? Not in the checked CTF sample: market matched hexadecimal conditionId. Gamma id identifies metadata, and book.asset\_id identifies the selected outcome token. In this profile