What a time to be a chess player! The Internet allows our game to thrive, powered by an ever-growing community of chess developers.

Did you know? The success of the Internet lies in open source. Every website, commercial or not, is mostly powered by open source software! Open source is about sharing ideas and code, so developers don't have to reinvent everything all the time.

While we all benefit from open source, not everyone chooses to contribute back. But the ones who do, these are the heroes who make chess software awesome. An example? Stockfish, the strongest chess engine, is open source. Therefore every chess website can use it!

Of course, Lichess itself is entirely open source. But let us review some great, lesser known, open source chess websites around.

Free Chess Club

https://www.freechess.club/ (source code)

Free Chess Club is a modern web-based interface for playing chess on FICS (Free Internet Chess Server), one of the oldest internet chess servers which split off from ICC way back in 1995.

Like FICS, Free Chess Club is fully free with no ads. It is also fully open-source including the front-end, the back-end and the infrastructure code. In addition to the website, there are cross-platform desktop clients based on Electron and mobile apps based on Cordova.

As you can perhaps tell, it was inspired by Lichess’ philosophy in many ways and has served as a handy alternative to play online chess on FICS. Our near term plans include supporting features such as puzzles, relay and lectures, and a possible migration to using “chessground” for the UI.

-- Free Chess Club author

Kung Fu Chess

https://www.kfchess.com/ (source code)

Kung Fu Chess is a variant of chess designed for the internet age. It brings the real-time strategy aspect of games like StarCraft, Command & Conquer, and Age of Empires to a classic setting. Both players move their pieces simultaneously, allowing them to attack on multiple fronts and react to the opponent's moves to gain an advantage. Being able to think on your toes in high-pressure situations is the key to victory!

-- Kung Fu Chess author

Chess Variants Training

https://chessvariants.training/ (source code)

Chess Variants Training is a website where you can improve your chess variant skills by solving variant chess puzzles. The site supports all variants that are on Lichess. For the variant puzzle creators amongst us, there is the ability to contribute your own puzzles to the site. And if variants are not exotic enough for you, you can also play Variant960 - variant games with a randomized back rank, a mix of variants and Chess960.

-- @programfox, Chess Variants Training author

Bughouse Chess

https://bughousechess.org/ (source code)

Bughousechess.org is an open-source website created for chess players to play Bughouse chess. Users may sign up, create, and play rated or unrated Bughouse chess games with other online players. The web application is written with React + Redux front-end and Node.js backend (using a PostgreSQL database).

-- Bughouse Chess author

Leela Chess Zero

http://play.lczero.org/ (source code)

Some people here probably followed Deepmind's AlphaGo, then AlphaGoZero and finally AlphaZero's achievements. However Google did not release the weights for all thoses networks, so a community has formed trying to reproduce and maybe improve the AlphaZero engine.

To do this, a distributed effort to play self-play games has started, and the training is done on a single powerful computer (It can update the weights in about 5 hours currently).

You can see the self-play ELO curve (not representative of real ELO) above.

If you want to help the project by sharing your GPU/CPU, think about following the instructions on the "Getting Started" section of the wiki.

Blindfold chess

https://chessinsights.org/blindfold (source code)

A minimalist tool play blindfold chess. You click on a move to make it, and that's really all there is to it! Playing blindfold is hard, but don't worry, there's a list of moves and a board to get you back on track if you get lost.

Lichess tactics generator

http://chesstacticsgenerator.vitomd.com (source code)

Generates tactics from your own lichess games. Enter your Lichess username and click generate. It will pull your last 50 games that have analysis in the blitz, rapid, classical category. This tactic generator uses the info that lichess attaches to your analyzed games. It will look for tactics that you or your opponent missed. These are the ones that have two consecutive Blunders moves, like your opponent left a unguarded piece and you didn't take it, so lichess will provide a variation in the second blunder move with the correct moves.

There's more!

For sure we forgot many great open source chess websites. Do you run one? Send it to us at contact@lichess.org! It qualifies if:

• It runs in a browser
• It's released under an open source license
• It's free to use, or it has a paid subscription model. Yes, commercial projects are allowed. It's not incompatible with open source.
• It has no ads
• It's about chess or chess variants

Thanks for reading. Let's build better chess tools together!