A.C.A.S (Advanced Chess Assistance System)

[!WARNING] A.C.A.S is currently in development. Expect bugs, especially on variants.

A.C.A.S (Advanced Chess Assistance System) is an open-source chess assistant (not a chess cheat), designed to help you make better moves using a chess engine. Just install the userscript, open the A.C.A.S GUI, and you're ready to go. No downloads necessary!

[!CAUTION] The use of A.C.A.S may violate the rules and lead to disqualification or banning from tournaments and online platforms. A.C.A.S is meant to be used as a real-time learning tool. Remember, struggling at chess doesn't mean you're unintelligent... it's not an IQ test, just a board game. And even IQ tests only measure certain aspects of your abilities. Use A.C.A.S fairly, be kind to other players.

▶️ Open A.C.A.S	⬇️ Install (GreasyFork)	💬 Discuss With Community

• Many built in WebAssembly engines (faster than JS)
• External engines (via an installable localhost server)
• Supports top chess sites (chess.com, lichess.org, etc.)
• Multiple suggestions, arrows, variants, fonts
• Multi-engine support, each with own settings
• Ability to modify any engine UCI options (e.g. ELO, depth, multiPV, skill)
• Visual board metrics (safe, contested, enemy squares, captured pieces)
• Move feedback and opponent predictions
• Render directly on external boards (or stay hidden via ghost mode)
• Audio TTS suggestions with adjustable speed
• Floating panel for stability and faster calculation
• Customizable themes (colors, fonts, textures)
• Chess variants supported (chess960, Fairy Stockfish variants)
• Translated into 30+ languages
• No anti-features on userscript

Used Libraries ❤️

Library	Description	License
Fairy Stockfish WASM	Chess engine (variants)	GPL-3.0
Stockfish WASM	Chess engine (main engine)	GPL-3.0
ZeroFish	WASM port of Lc0 + Stockfish	GPL-3.0
Maia-Chess	Human-like NN weights	GPL-3.0
Maia-Platform-Frontend	Maia 2 engine source	MIT
Lozza	Additional chess engine	MIT
COI-Serviceworker	Enables WASM on GitHub Pages	MIT
ChessgroundX	Chessboard UI (modified)	GPL-3.0
FileSaver	Save config files	MIT
bodymovin (lottie-web)	SVG animations	MIT
chess.js	Game logic (Maia 2)	BSD-2-Clause
onnxruntime-web	Run ML models in browser	MIT
Klaro!	Cookie consent manager	BSD 3-Clause
SnapDOM	DOM → image screenshots	MIT
UniversalBoardDrawer	Draw arrows on boards	GPL-3.0
CommLink	Cross-window communication	GPL-3.0
Bootstrap Icons	Icon set	MIT
Mona Sans	Font (GitHub)	SIL Open Font License
Rubik	Sans-serif font	SIL Open Font License
IBM Plex Sans	IBM typeface	SIL Open Font License
ws	WebSocket server library	MIT
Electron	Desktop app framework	MIT

There might be more, please let us know if anything is missing, thank you!

How does it work?

A.C.A.S (Tab #1)	Chess Website (Tab #2)
The engine runs in a completely separate tab from the chess game, keeping it fully isolated from the game page. The chess website cannot block or interfere with A.C.A.S.	A.C.A.S sends move data via CommLink, while the userscript displays the data on the chessboard using UniversalBoardDrawer. This requires the "Display Moves On External Site" setting to be enabled.

If you're having issues, please visit the troubleshoot page. Developers can visit the development page. Thank you!