
Internal Steam Web API documentation.
Steam API is a free Games & Comics API that requires no API key, is served over HTTPS and does not support CORS, so it should be called from a server.
Documenting the unofficial and internal Steam Web API
Details from github.com.

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Free Sudoku puzzle generation and embedding with images, solver links and interactive games
The Steam API is provided by Revadike (github.com). Documenting the unofficial and internal Steam Web API
Yes. The Steam 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 Steam API requires no authentication, so you can start making requests without signing up.
Not directly. The Steam API does not allow CORS, so call it from a server, serverless function or proxy instead of front-end JavaScript.
Yes. The Steam API is served over HTTPS, so it's safe to use in production.