Cryptocurrency Trading Platform.
KuCoin API is a free Cryptocurrency API that requires apiKey authentication, is served over HTTPS and has unconfirmed CORS support.
Introduction - KUCOIN API
Details from docs.kucoin.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.
Crypto futures prices, candles, funding, open interest, long/short and liquidations, 9 exchanges
The KuCoin API is provided by KUCOIN API (docs.kucoin.com). Introduction - KUCOIN API
Yes. The KuCoin 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 KuCoin API uses apiKey authentication, so you need to register for credentials before making requests.
CORS support for the KuCoin API is unknown. Test a request from the browser, and fall back to a server-side call if it is blocked.
Yes. The KuCoin API is served over HTTPS, so it's safe to use in production.