Provides detailed character and guild rankings for Raiding and Mythic+ content in World of Warcraft.
Raider API is a free Games & Comics API that requires no API key, is served over HTTPS and has unconfirmed CORS support.
Details from raider.io.

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The Raider API is provided by Raider.IO Developer API (raider.io).
Yes. The Raider 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 Raider API requires no authentication, so you can start making requests without signing up.
CORS support for the Raider API is unknown. Test a request from the browser, and fall back to a server-side call if it is blocked.
Yes. The Raider API is served over HTTPS, so it's safe to use in production.