The Polymarket API: market data, trading and Polymarket US

Source: Polymarket’s API overview. Real-time data comes over WebSockets: a public market channel for order-book updates and an authenticated user channel for your own orders. Its Data API v2, live since 4 September 2026, needs “no API key or authentication”.

Trading through the CLOB uses two layers. First your wallet signs a message (EIP-712, on Polygon) to create or derive API credentials — a key, a secret and a passphrase. Every trading request is then signed with those credentials (HMAC-SHA256), and each order is also signed by the wallet that authorises it. Accounts created on or after 4 May 2026 use what Polymarket calls a deposit wallet; older ones use proxy or Safe wallets, which the API still supports.

Keep the secret and passphrase as you would a password: with them, someone can trade your account.

• TypeScript: @polymarket/client. Python: polymarket-client. Both are the current “unified” SDKs listed in the SDK docs.
• The older clob-client and py-clob-client repositories are archived; Polymarket publishes a migration guide.
• Rate limits are per IP address and throttled rather than rejected — 4,000 requests per 10 seconds for Gamma in general, 300 for its markets list, 9,000 for the CLOB.
• Order placement also has per-signer limits by volume tier, from 40 orders a second; a rejected request returns 429 with a Retry-After header.

Polymarket checks the IP address of every order. Its geoblock endpoint (GET polymarket.com/api/geoblock) tells you whether yours is blocked, and “orders submitted from blocked regions will be rejected”. The docs list three groups: countries blocked entirely under US sanctions; countries, including the US, the UK, France, Germany and Australia, where the website and the API allow only closing existing positions; and a few — Ireland, Japan, the Netherlands, South Korea, and Malta for sports — restricted on the website but not the API. Using a VPN to get round this breaks Polymarket’s terms.

Fees apply to API orders as to any other: takers pay fee = contracts × fee rate × p × (1 − p), with the rate set by category, and makers pay nothing.

Polymarket US, the CFTC-designated exchange for US residents, has its own API: a public gateway (gateway.polymarket.us) for market data with no key, and an authenticated API (api.polymarket.us) for orders and accounts. To get keys, download the Polymarket US iOS app, complete identity verification and create them at polymarket.us/developer; requests are signed with Ed25519, and the secret is shown only once. The general limit is 25 requests a second, and Polymarket publishes Python and TypeScript SDKs for it. Accounts on polymarket.com and Polymarket US are not connected.

Outages and engine restarts are posted on Polymarket’s status page. For which venues offer an API at all, see prediction market APIs, ranked.