Cloud Compiler API is the only free API which compiles the source code provided by the user in the cloud and returns the output. Currently this API supports 70+ programming languages.
No authorization key is required to access this API. Anyone can directly access the API at the endpoints as given in the documentation.
Go through the documentation at http://cloudcompiler.esy.es/docs to get familiar with the API. If you have any issues or trouble using this API, please report it to us.