Chess Acuity

Chess Acuity turns any chess position into insight — entirely on your device.

Set up a position and Stockfish 17, running locally on your iPhone, shows you the best moves and lines. No account, no ads, no analytics, no internet connection required. The app is free and open source.

FOUR WAYS IN • From a photo — share a screenshot from any chess app or website, or pick one from your photo library. A built-in recognizer reads the board on-device and sets up the position. • From a game — paste a PGN, step through the moves, and analyse any position along the way. • By hand — set up the board in a clean, fast editor. • By FEN — paste a position directly.

ANALYSIS • Powered by the Stockfish 17 chess engine, running natively on your device. • Multiple lines (MultiPV) with evaluations, searched by depth or thinking time. • Step through any line move by move on the board. • Plain-language explanation of the engine's choice.

PLAY • Play a full game against Stockfish at eight strength levels. • Take a hint when you're stuck, then hand the finished game straight to the analyser.

PRIVATE BY DESIGN Everything — board recognition, engine analysis, move explanations — runs on your device. The app makes no network requests and collects no data. Screenshots you import are processed locally and never uploaded.

OPEN SOURCE Chess Acuity is free software under the GNU GPLv3. The complete source code is available at github.com/alexostar/chess-acuity-app.

FAIR PLAY Chess Acuity is made for study and review. Please don't use it for assistance during live or rated games — that breaks the fair-play rules of every chess site and spoils the game for everyone.