RESTful Quran API with multiple languages.
Quran API is a free Books API that requires no API key, is served over HTTPS and supports CORS, so it can be called from the browser.
API documentation for OpenAPI versions 2.0/3.0/3.1
Details from quran.api-docs.io.

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Free REST API for the Runyankore-Rukiga Bible — 66 books, 31106 verses
The Quran API is provided by API Docs (quran.api-docs.io). API documentation for OpenAPI versions 2.0/3.0/3.1
Yes. The Quran API is listed in the Books 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 Quran API requires no authentication, so you can start making requests without signing up.
Yes. The Quran API supports CORS, so front-end JavaScript can call it directly.
Yes. The Quran API is served over HTTPS, so it's safe to use in production.