The Polymarket API
Last updated · how we verify
The Gamma API at https://gamma-api.polymarket.com is public and needs no
authentication — you can fetch markets, events and prices immediately. Use Gamma for discovery and
metadata, the CLOB API for order books and trading, and the Data API for positions and history. Only the
latter two need credentials.
Three APIs, three jobs
| API | Use it for | Auth |
|---|---|---|
Gammahttps://gamma-api.polymarket.com | Market and event discovery, metadata, prices | None |
| CLOB | Order books, placing and cancelling orders | Required |
| Data | User positions and trade history | Required |
Fetching open markets
The markets endpoint is https://gamma-api.polymarket.com/markets. A minimal request for the highest-volume open
markets:
GET https://gamma-api.polymarket.com/markets?closed=false&limit=10&order=volumeNum&ascending=false
Useful parameters: closed to filter resolved markets, limit and
offset for paging, order with ascending for sorting, and
slug to fetch a specific market.
It is a free public endpoint. Cache aggressively, request only the fields you need, and do not poll in a tight loop — this site refreshes its own live-markets block once a day on a cron and that is ample for editorial use. Treating a free API considerately is how it stays free.
What we do with it
Live from the Gamma API
Yes-side probability, highest-volume open markets. Refreshed daily from Polymarket’s public Gamma API.
This block is regenerated daily by a scheduled build, which is also what keeps the
lastmod in our sitemap honest rather than a hardcoded constant.
Availability varies by jurisdiction. 18+. Event contracts carry risk of loss.
You appear to be in the US. Polymarket’s international exchange blocks US IP addresses — use Polymarket US, the CFTC-regulated exchange, instead. See what’s available in your state.
Things worth building
- A fee calculator using
fee = shares × feeRate × price × (1 − price)with the per-category rates from the fee schedule. - Cross-venue price comparison against Kalshi on equivalent markets.
- Resolution-criteria alerts for markets whose wording is ambiguous.
- Maker-rebate tracking to measure your effective negative fee rate.
Questions
Is the Polymarket API free?
The Gamma API at https://gamma-api.polymarket.com is public and requires no authentication for market discovery and metadata. Trading through the CLOB API requires credentials and a funded wallet.
Which API should I use?
Gamma for market discovery and metadata, the CLOB API for order books and trading, and the Data API for user positions and trade history. Most read-only projects need only Gamma.
Do I need an API key?
Not for Gamma. It is entirely public. Trading endpoints do require authentication.
How do I get current prices?
Query the markets endpoint and read the outcome prices. For live order-book depth rather than last prices, use the CLOB API.
Related
Fee formula
What to implement in a calculator.
Reading prices
Converting price to probability.
Guides
Getting an account set up.
FAQ
Everything else.
All figures on this page verified 17 August 2026 against primary sources where reachable. Unconfirmed values are marked.