Manifold API

What it is

The whole of Manifold, exposed. Fifty-odd documented endpoints cover users, portfolios and portfolio history, topics, questions, search, probabilities, positions, trades, comments, leagues and the transaction ledger, plus a perpetuals surface with its own oracle price and price series endpoints. Every read is keyless; every write takes a single Authorization: Key header from a key you generate on your own profile page.

What makes it unusual in this category is that the server is the same MIT-licensed repository the site runs on. When the documentation is ambiguous, common/src/api/schema.ts in manifoldmarkets/manifold is the actual contract — parameters and return types, not prose — and the docs page itself is a Markdown file in that repo that you can send a pull request to. The default branch was last pushed to on 18 September 2026.

Real time is a WebSocket at wss://api.manifold.markets/ws with a topic-subscription protocol, including a per-market topic for updates to resting limit orders. It needs a ping every 30 to 60 seconds; go quiet for 60 and the connection is closed.

Availability

No account is needed to read and no identity check to write: a key belongs to a Manifold account, and a Manifold account is an email address. There is no geographic gate on the API host, which answered this machine without credentials on 19 September 2026.

The constraint here is not jurisdictional, it is contractual. Use of the API is subject to the site's terms, which permit bots, automated trading systems and integrations, prohibit scraping the site by any means other than the API, prohibit circumventing rate limits, and reserve the right to suspend access for abuse or excessive usage. The AI-training clause is the one most likely to matter to a reader here — see Limitations.

Pricing

Free, with no plans, no metering and no paid tier. The only charge documented anywhere in the API reference is internal to the play-money economy: a comment placed through the API costs M1.

Because the currency is mana and mana cannot be withdrawn, there is no taker fee, no maker rebate and no settlement fee to record on this card — the economics block is null rather than zero on purpose. What a position costs you is the AMM's price impact, and that is a property of the question rather than a fee schedule.

The rate limit is the real ceiling: 500 requests a minute per IP, shared across every endpoint.

Markets & resolution

Anything anyone opens, which in practice is every category this catalogue tracks and a long tail that none of the money venues would list. The API is also how questions get created and resolved — POST /v0/market and POST /v0/market/[marketId]/resolve are ordinary endpoints, and the account that created a question is the account that settles it. Only moderators and staff can annul one to N/A.

That is the whole difference between this feed and every other one in the category. A price here is a crowd's estimate priced in a currency that buys nothing, and the resolution behind it is one person's judgement rather than an exchange's rulebook or an oracle vote. Treat a Manifold probability as a forecast, not as a quote.

Two naming traps that will bite the first integration. A topic is called a group in the code and in the API, not a tag. A question is a contract in the code and sometimes a market in the API, and both spellings appear in the same document. All times are UNIX milliseconds.

Integrations

REST plus the WebSocket, and nothing else first-party: there is no official Python or TypeScript client, no MCP server and no SDK published by the vendor. The community packages that exist are not named in the documentation, which is the honest way to read that absence.

Pricing mechanics leak into the API in a way worth knowing before writing an execution path. Manifold is a CPMM automated market maker with resting limit orders on top: an order carrying limitProb fills against the curve and against other people's unfilled orders up to that price, and whatever is left rests until it is cancelled or expires. expiresAt and expiresMillisAfter are parameters on the order itself. Open orders come back from the trades endpoint with kinds=open-limit, including on closed and resolved questions.

Limitations

• It is alpha, and says so. The documentation's own caution block warns that things may change or break at any time, and that the legacy manifold.markets/api host will disappear eventually.
• The bulk dumps are two years stale. The free markets, trades and comments archives on the data page are dated 6 July 2024, and there is no newer public dump. Current history means paging the API.
• Commercial AI training needs a licence. Academic, personal and non-commercial use of API data is permitted; training models for commercial purposes is not, without a separate data licence from the vendor.
• Nothing here is money. No withdrawal, no settlement in dollars, and no regulator — which is the point, and which rules this feed out for anyone pricing a real position.
• One key per account, refreshed rather than rotated: generating a new one invalidates the old.
• No official client library in any language, so the signing, retry and pagination code is yours.

Alternatives

For the same shape of data with money behind it and no key to read, the Polymarket Gamma API and the Kalshi API are the direct comparisons. If Manifold is wanted alongside other venues in one schema, FinFeedAPI normalizes it with eight others, at the price of a bill per request. And if what is actually wanted is a scored forecasting record rather than a tradable price, the platform itself — Manifold — publishes its own calibration, and Metaculus is the reference point for that job.