Lichess talks to [Stockfish 4](http://stockfishchess.org/) using a [FSM Actor](https://github.com/ornicar/lila/blob/master/modules/ai/src/main/stockfish/ActorFSM.scala) to handle AI moves and analysis.
It uses [MongoDB 2.4](http://mongodb.org) to store about 15 million games, which are indexed by [elasticsearch 0.90](http://elasticsearch.org).
> I am **not** happy to see lichess clones spreading on the Internet. This project source code is open for other developers to have an example of non-trivial scala/play2/mongodb application. You're welcome to reuse as much code as you want for your projects, and to get inspired by the solutions I propose to many common web development problems. But please don't just create a public lichess clone. Also, if you are building a website based on lichess, please mention it in the footer with `Based on <a href="http://lichess.org">lichess</a>`. Thank you!
> Also note that if I provide the source code, I do **not** offer free support for your lichess instance. I will probably ignore any question about lichess installation and runtime issues.
Big thanks go to lichess community for the support, inspiration, bug reports, and [amazing translation efforts](http://lichess.org/translation/contribute).
Special thanks go to:
- [Mephostophilis](http://lichess.org/@/Mephostophilis) for writing [Lichess Wiki](http://lichess.org/wiki), leading the cheater hunt, moderating the site, reporting countless bugs, and contributing to the codebase
- [Smiling Bishop](http://lichess.org/@/smiling_bishop), [legend](http://lichess.org/@/legend), [mb](http://lichess.org/@/mb) and all the moderators who spent time keeping the site enjoyable
- [Evropi](https://github.com/evropi) for contributing to the wiki and animating #lichess IRC channel