Chess board scanner: photo to FEN in your browser

What a chess board scanner does

A chess board scanner turns a picture of a chess position into notation a computer can use. It locates the board in the image, corrects the perspective so the board is square again, decides what stands on each of the 64 squares, and writes the answer out as a FEN string.

FEN (Forsyth–Edwards Notation) is the one-line text format every chess program understands. Once you have the FEN you can paste the position into an engine, a database, a study, or a new game. It also records whose turn it is, the castling rights, and the en passant square, which is why a scanner asks you to confirm those.

Snap That Piece uses custom machine-learning models, designed to run on mobile devices, to detect the board and classify every piece.

How to get the FEN from a photo of a chess board

Open the web app, photograph the board, wait a few seconds for the position to come back, then check it and copy the FEN. There is nothing to install and no setup beyond a free account.

1. Open the scanner

   Go to app.snapthatpiece.com in any browser on your phone, tablet or desktop and sign in with a free account.

2. Take or upload a photo

   Use the camera, or pick a picture you already have. Photos straight off an iPhone in HEIC work as they are, with no conversion.

3. Get the whole board in frame

   All 64 squares need to be in the shot. Shooting from above rather than across the table keeps the pieces from hiding each other.

4. Wait for the position

   The board is found, flattened to a square, and every piece identified. This takes a few seconds.

5. Check it and copy the FEN

   Set the side to move and the castling rights, and tap any square that is wrong to fix it in the board editor. Then copy the FEN, or go straight to analysis.

What it handles

Snap That Piece is built for boards that exist in the world rather than diagrams that exist on a page. Point your camera at a tournament set, a wooden board at home, a diagram in a book, or a position on a screen; the board is detected, every piece is recognized, and you get the FEN in seconds.

• Physical sets photographed at an angle. A normal phone photo taken from a player’s seat is the expected input, not the difficult case.
• Tournament and club equipment. Plastic tournament sets and wooden boards, in the sizes and colours clubs actually use.
• Book and magazine diagrams. Printed 2D positions photographed off the page.
• Screens and screenshots. A position on a monitor, a stream, or an image saved from another site.
• Photos as they come off the phone. Including HEIC, and including boards that are not perfectly square to the camera.

When recognition struggles

Recognition is good, not perfect, and some photographs are much harder than others. The board editor exists because corrections are expected rather than exceptional, and these are the cases that cause most of them.

• A cropped board. A square outside the frame cannot be read. This is the single most common cause of a wrong position.
• A steep angle. Photographed from low down, the back rank hides behind the pieces in front of it.
• Something over the board. A hand reaching in, a scoresheet, or a coffee cup covering squares.
• Hard light. Strong glare on lacquered pieces, or a room dark enough that pieces and squares run together.
• Unusual sets. Highly stylised, themed or novelty pieces are further from anything the models have seen.

If the position is symmetrical enough that the board’s orientation is genuinely ambiguous, the app says so rather than guessing silently, and you can flip it in one tap.

We do not publish an accuracy percentage. A single number would flatter the easy cases and mislead about the hard ones, and it would say nothing useful about the photo you are actually about to take.

After the scan

Most scanners hand you an analysis board and stop there. Snap That Piece is built so the scan is the beginning: the position you photographed becomes something you can study, play out, or send to someone else.

• Analyze with Stockfish. Stockfish runs on-device in your browser, with depth presets from fast to deep, an evaluation bar, and best-move arrows.
• Play it out against a bot. Continue the position against Stockfish, or against Leela Chess Zero running the Maia networks: human-like opponents from 1100 to 2200 Elo that misplay the way a real player at that rating does. Play Leela Chess Zero.
• Play a friend. A share link opens the position as a live game with clocks, draw offers and rematches.
• Take it elsewhere. Copy the FEN, export a played game as PGN, or open the position in the Lichess analysis board, the Lichess board editor, or Chess.com analysis.

No board in front of you? Play GM Equal Positions from real grandmaster games, or start from a Chess960 starting position.

What it costs

Nothing. Scanning a board, analyzing with an engine, and playing online are all free, with no ads and no paid tier.

Browsing snapthatpiece.com needs no account at all: the Chess960 generator, the GM Equal Positions browser, and the Knight and Pawn Race mini-games all run without one. Scanning a board, saving positions, and playing online in the web app need a free account.

Snap That Piece is live now as a free web app at app.snapthatpiece.com. An iOS app is coming soon to the App Store, and will do recognition entirely on-device.

Questions