Real-time Crypto Currency Exchange Rates.
Coinlayer API is a free Cryptocurrency API that requires apiKey authentication, is served over HTTPS and has unconfirmed CORS support.
Access real-time and historical crypto data with Coinlayer’s powerful Crypto Currency API. Built for speed, simplicity, and performance—20ms response time, easy integration, and extensive documentation.
Details from coinlayer.com.

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Geocode an address, validate an email, track a flight or pull stock data with one account, one dashboard and one API key.
Get the list of all traded assets in the exchange
The Coinlayer API is provided by Coinlayer (coinlayer.com). Access real-time and historical crypto data with Coinlayer’s powerful Crypto Currency API. Built for speed, simplicity, and performance—20ms response time, easy integration, and extensive documentation.
Yes. The Coinlayer 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 Coinlayer API uses apiKey authentication, so you need to register for credentials before making requests.
CORS support for the Coinlayer API is unknown. Test a request from the browser, and fall back to a server-side call if it is blocked.
Yes. The Coinlayer API is served over HTTPS, so it's safe to use in production.