TIO – online interpreters for programming languages

This seems to be the source code for it: https://github.com/TryItOnline/tiosetup

> https://tryitonline.net is a web site that started out as a place for hosting solutions to code golf puzzles presented on http://codegolf.stackexchange.com/. It can be used by anyone for free to quickly try out and share code snippets, with or without code golf in mind alike, in a big number of practical and recreational programming languages.

Wow! It is amazing how many languages are supported by this.