Polymarket Gamma API

What it is

The read half of Polymarket. Gamma is a plain REST service at gamma-api.polymarket.com that answers what is listed and what it means: events and their child markets, the series a recurring market belongs to, sports fixtures and teams, tag taxonomies, and a search endpoint. Every record carries the fields a catalogue needs — slug, condition ID, outcome token IDs, start and end dates, the resolution rules text, and the liquidity and volume figures Polymarket publishes about itself.

It is a separate product from the CLOB API and is bought by different people. Gamma is what you call to build a page, a screener, a research dataset or a market index. Nothing in it prices an order or places one, and no part of it requires a wallet.

The two identifiers that matter come out of here: the conditionId for the market and the token ID for each outcome. Both are what every other Polymarket surface is keyed by.

Availability

Unrestricted as far as Polymarket documents it. The endpoints take no credentials, so there is no account to be refused and no jurisdiction attached to a request.

That is worth separating from the platform underneath. Polymarket's international site tells a US visitor that trading is blocked and offers to continue in view-only mode, pointing at Polymarket US — a different entity, operating as a CFTC-designated contract market, with its own documentation and its own API. Gamma is the international platform's data service. A US reader may read it; what they may not do is trade the markets it describes on that platform.

The practical consequence for anyone building: Gamma will happily serve you a market your users cannot take a position in. Availability has to be enforced by your application, because the data layer does not carry it.

Pricing

Free, with nothing to buy. Polymarket sells no data plan, no tier and no key for the read endpoints, and the builder programme is about routing orders rather than about reading markets.

The limit that bites instead is undocumented. Polymarket's builder tiers list API rate limits as Standard for unverified and verified builders and Highest for partners, without stating what any of those are in requests per second. Treat the absence as a reason to implement backoff, not as an absence of limits.

Markets & resolution

Gamma describes markets it does not resolve. Resolution on Polymarket runs through the UMA optimistic oracle: an outcome is proposed against a bond (the docs give roughly 750 pUSD), there is a two-hour challenge window, a first dispute triggers a second proposal round, and a second dispute escalates to a vote of UMA token holders after a 24 to 48 hour debate period. Undisputed, that is about two hours; disputed, Polymarket's own timeline says four to six days.

Two fields on a Gamma record are worth more attention than they usually get. The rules text is where the actual source and the edge cases live — the question title is only the question. And a UMA vote can return "Unknown", in which case the market resolves 50/50 and every token, on both sides, redeems at 50 cents. Code that assumes a binary payout will mis-book that day.

Markets are grouped as events with child markets, which is the shape that surprises people coming from an exchange API: one event, many tradeable questions, each with its own pair of outcome tokens.

Integrations

REST and JSON, cursor-paginated through the keyset variants of the list endpoints. Polymarket publishes unified SDKs that cover this surface — the Python one is polymarket-client, whose AsyncPublicClient lists markets with no credentials — and an OpenAPI description of Gamma is linked from the documentation index.

There is no WebSocket here. Real-time on Polymarket comes from the CLOB market channel and from a separate live-data stream, both documented on the trading side.

Limitations

• No order book, no prices beyond what the record carries. Any question about the current spread goes to a different host.
• No price history. The series endpoint lives on the Data API, not on Gamma, and is keyed by token ID rather than by market slug.
• No published rate limit. You will discover yours in production.
• No stream. Keeping a large catalogue fresh means polling, and the polling budget is the undocumented number above.
• Volume and liquidity figures are Polymarket's own. They are the platform's numbers about the platform's markets, computed however Polymarket computes them, and nothing in the API explains the method.

Alternatives

For prices, books and order placement on the same venue, the sibling product is the Polymarket CLOB API — same markets, different preconditions. If what you want is a regulated US exchange with a documented rate-limit table and settled-market archives, the Kalshi API is the closest equivalent in shape. On Base, with its own REST and WebSocket surface, Limitless API covers a smaller and much shorter-dated market list.