Open-Source Chess Software List

Everything here is ad-less and free as in price. So, you can just find some interesting stuff :). Links for navigation through page. Learning websites, fun projects, chess engines, playing servers, GUI, Other. Also, you can check out Lichess based websites and links team, I found some stuff there.

I'll keep this list updated.

Learning websites

Blitztactics

This website has features similar to Lichess Puzzle Storm and Streak but more solving modes (Haste, Three, Countdown, Speedrun etc.) and Leaderboard.
Also you can practice there some endgame positions (Lucena, Bishop and Knight Checkmate, Reti's idea in pawn endgames). Source code + Their Discord

Chessdriller

This website helps you to memorize your opening variations using data from your lichess studies. Similar to Chessable feature of spaced repetition/review. Liked it very much. Source code

aidchess.com

Similar to the project above but interface is different. Source code

OpeningTree

Prep against your opponents by checking their games from chess.com and lichess. You already can view one's player lichess games using "player" button in opening explorer on Lichess itself. Source Code

Chessdb.cc

Advanced search for the top chess games in the world. Source code

Blunder-Bomb

Try to figure out when exactly player made a blunder! Can be pretty hard sometimes :)

Listudy.org

Website with different features, but what I find interesting is blindfold ("pieceless") tactics. You can also practice some endgame positions there as well.
Source code

Chessort.com

Sort 4 moves in the position from best to worst. Website is in beta I think, so some puzzles are a bit strange, some good. Developer had a blog on lichess about this website. Source code

Chessinsights.org

Play Blindfoldchess with different levels (1100-3100) Stockfish. Source code

Chessli2

For Chess Improvers who like Anki, working with SCV files. Not sure I am the one, but seems like a good project. Source Code

Syzygy-tables

Some interesting stats on Syzygy 7-piece tablebases. Lichess had a blog on these tablebases. You can download tablebases from lichess (for atomic and antichess variants too). Source code (for the website)

Rather fun ones

Freopen.org (World Chess Champion Number)

This way you can know how far are you from beating Magnus on Lichess. It's of course oversimplification but you can visit the website to undestand the concept or read this lichess blog from author. Source Code

Lichievements

Check your "achievements" on Lichess based on your games. Source code

Perk Chess

Browser extension to gamify your lichess experience (achievements, levels, perks etc.) Source code

Chessstamps.app

Check for your rare openings ("chess stamps") that you play on lichess!

Chess Engines (First names aren't new, but some can be interesting)

Stockfish

Best by Test Chess Engine that you probably already know :) Still I used it for years but never checked their website, when I went there I was pleasantly surprised, it looks very cool. Their blog on lichess and Source Code. SF 17 is already availaible on Lichess by the way!

Lc0

AlphaZero but better :) Same for Stockfish, I liked the website. You can find and play Leela Chess Zero giving you odds on Lichess Bots Page. Source Code

Maiachess

A human-like neural network chess engine. Lichess had a blog about this project 4 years ago. Basically neural network analysed games of lichess players 1100-1900 and tries to imitate human-style. You can find and play Maia 1100, 1500, 1900 on Lichess Bots Page. Source code

Berserk

Berserk 13 is very strong open-source engine (if I understand ranking correctly it's #3 on October 2024). Not gonna lie, I am not much into engine playground :) Still Guts Art on their Github is pretty cool. We need more engines named after animated series!

Lizard

Komodo but better! Design-speaking only though (for now at least) I mean their logo on Github is pretty funny, I'll even insert it. It's #13 as October 2024

Other Chess Engines

Honestly when I thought of adding this section I didn't knew that there whole a lot of open-source engines. I don't understand much in it so other wil be just written here with not much description Patricia (most agressive chess engine), Patricia lichess bot, Caissa, Ethereal, Alexandria, RubiChess, Seer, Titan, Obsidian, Halogen, PlentyChess, Viridithas, Clarity, Arasan (Arasan Lichess Bot). These are all strong engines, but how much strong and how useful they can be for those who are not chess programming enthusiasts is a question for me, since I don't work with engines deeply. Off-topic for this blog, but it is interesting field, like will some engine dethrone Stockish? We'll see but there's wiki for those interested in chess-related programming.

Variant Engines (Fairy-Stockfish and CrazyAra)

Fairy-Stokfish is very strong variant engine with support for a lot of variants. In some variants strongest. Supports custom variants. Used in lichess analysis for variants. Source code.
CrazyAra is strong crazyhouse engine. It has profile on lichess. Source code

Playing Servers (variant ones too)

I'll start this section with saying that I consider Lichess a best server currently, but still you can find something interesting on other websites, problem with them is low-userbase usually.

Free Internet Chess Server

Modern. FICS. This project is pretty old, I know that ZH-goats played there before lichess lol. Their modern website is minimlist and alright. Project also has Android App on Google Play and F-Droid

Bughouse.pro

Open-source website where you can play Bughouse! Well, it's in beta, but still. Project Discord Server and Source Code

Playstrategy.org

Lichess fork (hosted in the UK) with lots of variants. It has chess also. Userbase is much lower, but project is far from dead. All about board games and their variants like Chess-based, Draughts-based, backgammon, amazons, Go-based, Shogi-based etc. You can find all variants here.
One feature that I like there is Medley, when variant/game changes throughout the tournament/arena.

Pychess.org

All about variants, but it has different ones from playstrategy. Like 960 version of a lot of varians. Also signing in requires Lichess Account (not a big problem since you already here). Supports Variant Puzzles. Website has also it's own fork website for testing even more variants (you can read motivation behind it here

Other

Cannot not mention Lichess forks for Draughts lidraughts.org and for Shogi lishogi.org

GUI (Graphical User Interface) Chess Apps

GUI - App on your device, where you can analyze chess with different engines, store your pgn-files. Chessbase probably most well-known example, but it's closed-source and paid.

En Croissant

"The Ultimate Chess Toolkit" with cool logo. It's certainly very good and in active development, has lots of features. Developer also had a little blog about this software on Lichess. Source Code

DroidFish (Android)

Use Stockfish on Android. You can get it on Github and F-Droid

Nibbler

Chess GUI with extra features for Leela Chess Zero use. it works with other engines like Stockfish, too. Source Code

PyChess GUI

PyChess GUI, not to be confused with the pychess variants website, has features for analysis and game play, supports several chess variants for 8x8 boards, and is compatible to UCI and CECP chess engines (including variant ones). Source Code

Lucas Chess (R)

Lucas Chess (R) is a GUI of chess to train in different ways (tactics, endgames, openings), play chess against engines and analyze your games. Organize tournaments between engines as well. Source Code

Cute Chess

Cutechess mainly a chess engine tournament manager, with both a command line and a graphical user interface. Also supports game play against engines, but does not have analysis features. Chess variants are also supported. Source Code

LiGround

LiGround is a modern, cross-platform chess variant GUI for lichess variants and regional variants (Shogi, Xiangqi, Janggi, Makruk). As it is a rather new project the set of features is rather limited, but working well for basic analysis and game play. Compatible with UCI engines, especially Fairy-Stockfish. Chess itself supported too. Source Code

ChessX

Looks like a good chess software in active development. Source Code

WinBoard/XBoard

WinBoard/XBoard is an old but very feature rich chess and variant GUI supporting a large variety of chess variants, including user/engine defined games. Not as modern and stable as other GUIs, but still one of the most used variant GUIs. Compatible with CECP/XBoard engines. Endorsed by GNU

Scid

Shane's Chess Information Database (Scid) is a powerful Chess Toolkit, with which one can create huge databases, run chess engines, and play casual games against the computer. Kind of an Dinosaur thing, but I remember using Android app myself. Scid vs. PC (fork of the project in the title) and Client on Android on F-Droid, Github and Google Play.

Other (tools, variants)

Lichess Databases - All games (This website also has puzzle database, some interesting links at the bottom, stockfish evaluations database) and Elite Lichess Database (2400+ Lichess Ratings), Lichess Puzzles Sorted by rating

Lichess Arena Rankings - you can check some records and a lot of stuff

didiblunder.com - open-source clone of chess.com feature, chess review

FICS Database and FICS Bughouse Database

Chess Variant Hub - wanna get into different variants of chess, regional ones as well? That's right place to find some useful info. Very good website.

Chess960 Position Randomizer

Chessvariants.training - Check some community variant puzzles. Though I should say some are faulty. Also possible to play 960 version of variants. Source Code

Prettierlichess browser extension (Source) and Lichess Tools Browser Extension (Source). First one makes style difference, second actually adds some extra features, you can read developer blog on Lichess

ChessCam - Record a chess game live and upload the PGN to Lichess. Source Code

Coronate is a web app for managing Swiss-style chess tournaments. Source Code

Blitz: Fischer Chess Clock - A minimalist Fischer chess clock for Android. Get in on F-Droid, Github and Google Play

Kung Fu Chess is a real-time chess game where players don't take turns. A player may make a move at any time, but pieces have a travel speed and a cooldown period. There are 2 websites www.kfchess.com and kungfuchess.org. Both open-sourced 1st and 2nd

Open Chaos Chess for Android is a variation of chess where you can pick the piece that moves, but the moves are random. As such, you no longer win by checkmates. Instead, you win by eliminating your opponent's pieces. Quite funny one. Get app on F-Droid and Github.