Fake data for testing and prototyping.
JSONPlaceholder API is a free Test Data API that requires no API key, is only available over HTTP and has unconfirmed CORS support.
Free fake and reliable API for testing and prototyping. Six resources, all HTTP methods, no signup.
Details from jsonplaceholder.typicode.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.
Generate Random startup ideas
The "lorem ipsum" generator that doesn't suck
Yes. The JSONPlaceholder API is listed in the Test Data 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 JSONPlaceholder API requires no authentication, so you can start making requests without signing up.
CORS support for the JSONPlaceholder API is unknown. Test a request from the browser, and fall back to a server-side call if it is blocked.
No. The JSONPlaceholder API is only available over plain HTTP, which browsers block on HTTPS sites. Call it from a server instead.