
Reference for 5th edition spells, classes, monsters, and more.
Dungeons and Dragons API is a free Games & Comics API that requires no API key, is only available over HTTP and does not support CORS, so it should be called from a server.
REST + GraphQL API for the 5e SRD database
Details from dnd5eapi.co.

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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.
Includes all monsters and spells from the SRD (System Reference Document) as well as a search API
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Yes. The Dungeons and Dragons API is listed in the Games & Comics 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.
No. The Dungeons and Dragons API requires no authentication, so you can start making requests without signing up.
Not directly. The Dungeons and Dragons API does not allow CORS, so call it from a server, serverless function or proxy instead of front-end JavaScript.
No. The Dungeons and Dragons API is only available over plain HTTP, which browsers block on HTTPS sites. Call it from a server instead.