
Online Compiler for Various Languages.
Codex API is a free Development API that requires no API key, is served over HTTPS and has unconfirmed CORS support.
CodeX is an online compiler for various languages like Java, C++, Python, etc. Execute code in various languages on your own website for free with the CodeX API!!!
Details from github.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.
Get IP Address, Timestamp, User Agent, Country Code, IATA, HTTP Version, TLS/SSL Version & More
Free and simple counting service. You can use it to track page hits and specific events
The Codex API is provided by Jaagrav (github.com). CodeX is an online compiler for various languages like Java, C++, Python, etc. Execute code in various languages on your own website for free with the CodeX API!!!
Yes. The Codex API is listed in the Development 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 Codex API requires no authentication, so you can start making requests without signing up.
CORS support for the Codex API is unknown. Test a request from the browser, and fall back to a server-side call if it is blocked.
Yes. The Codex API is served over HTTPS, so it's safe to use in production.