Provides information about Player stats , Match stats, Rankings for Dota 2.
Dota 2 API is a free Games & Comics API that requires apiKey authentication, is served over HTTPS and has unconfirmed CORS support.
Details from docs.opendota.com.

Unified API suite · now live
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
The Dota 2 API is provided by OpenDota API (docs.opendota.com).
Yes. The Dota 2 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.
Yes. The Dota 2 API uses apiKey authentication, so you need to register for credentials before making requests.
CORS support for the Dota 2 API is unknown. Test a request from the browser, and fall back to a server-side call if it is blocked.
Yes. The Dota 2 API is served over HTTPS, so it's safe to use in production.