APIs for authorization and access control.
Warrant API is a free Authentication & Authorization API that requires apiKey authentication, is served over HTTPS and supports CORS, so it can be called from the browser.
Warrant has been deprecated and is now WorkOS FGA (Fine-Grained Authorization).
Details from warrant.dev.

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Geocode an address, validate an email, track a flight or pull stock data with one account, one dashboard and one API key.
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The Warrant API is provided by Warrant —> Now WorkOS FGA (warrant.dev). Warrant has been deprecated and is now WorkOS FGA (Fine-Grained Authorization).
Yes. The Warrant API is listed in the Authentication & Authorization category of the public-apis directory, which only includes APIs that are free or have a free tier. Check its documentation for rate limits and paid plans.
Yes. The Warrant API uses apiKey authentication, so you need to register for credentials before making requests.
Yes. The Warrant API supports CORS, so front-end JavaScript can call it directly.
Yes. The Warrant API is served over HTTPS, so it's safe to use in production.