Cryptocurrency Trading Platform.
Coinbase Pro API is a free Cryptocurrency API that requires apiKey authentication, is served over HTTPS and has unconfirmed CORS support.
Details from docs.pro.coinbase.com.

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Cryptocurrency Trading Platform
The Coinbase Pro API is provided by Coinbase Developer Documentation (docs.pro.coinbase.com).
Yes. The Coinbase Pro API is listed in the Cryptocurrency 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 Coinbase Pro API uses apiKey authentication, so you need to register for credentials before making requests.
CORS support for the Coinbase Pro API is unknown. Test a request from the browser, and fall back to a server-side call if it is blocked.
Yes. The Coinbase Pro API is served over HTTPS, so it's safe to use in production.