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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 ratingEditorial assessment
Read CLOB price and book documentationdocs.polymarket.com
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Provider documentation for public market-data queries.

What is Polymarket CLOB API?

Public book data includes bids, asks and trading constraints, while reference endpoints provide midpoint, spread and last-trade information. Read the price side and identifiers before using a 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.

Features and coverage

  • 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.

Workflows with Polymarket CLOB API

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

Establish credentials and exact request signing, track order state and implement cancellation and reconciliation before automating order generation.

Validate the handoff

Compare asset_id with the selected token and market with conditionId. Retain the snapshot timestamp; a successful read does not show an order would fill at that 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.

Getting started

Before you start: The documentation describes best bid/ask levels at the end of book arrays.

  1. Discover the market and labeled outcome-token IDs through Gamma.
  2. Make a public book or price request.
  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.

The documented arrays place the best bid and ask at their last entries; do not assume the first level is best.

CLOB API base endpoint

Useful links

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.

A closer look

Ratings & reviews

Editorial rating
4.0/ 5
0 user reviews
PredictionToolkit editorial

Our take on Polymarket CLOB API

Direct books and explicit authentication layers provide a strong integration foundation. Identifier mapping, price sides and order conventions still need careful implementation.

Based on documented features, setup and access terms. How we rate

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Guides and workflows

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.