About stockfish.io
stockfish.io is an independent chess interface powered by the open-source Stockfish engine. It is not the official Stockfish project and is not affiliated with the Stockfish developers.
Engine: Stockfish 19 / Stockfish.js. See source & licence information.
Local chess analysis
The engine runs on your device. Positions and imported PGN files are processed locally; they are not sent to a chess-analysis server. There is no account or cloud game storage. Export your PGN before reloading or leaving the page if you want to keep a game.
PGN and position editing
One game and its main line are supported per PGN import. Supported headers and the result are retained; comments, annotations and variations are omitted. This is not a lossless PGN editor. Export includes the full current line, even when you are viewing an earlier move.
The position editor checks kings, pawns, material, basic promotion feasibility, checks, castling rights and en passant metadata before analysing. These checks do not prove that every accepted position is historically reachable. Cancel restores the original game and history position; applying a changed arrangement starts a new line after confirmation.
Importing a board image
Open FEN / PGN → Import image to select, drop or paste a PNG, JPEG or WebP. The importer recognises conventional 2D screenshots and diagrams on your device. You can adjust four crop corners, rotate the source, choose among detected boards, and correct every square before loading. Flat-diagram perspective correction is experimental; photographs of physical 3D chess pieces are not supported.
Check all pieces and coordinates, even when no squares are flagged as uncertain. The orientation suggestion can be wrong, especially without pawns. Choose the side to move explicitly. Castling and en passant default to none, and the counters to 0 and 1, as visible assumptions about unknown history. Castling rights affect legal moves and analysis; change them if you know the history. A picture cannot recover the preceding game or draw history.
Image processing sends no image, filename, image metadata or recognised position to an inference server. Recognition assets download from this site when used (about 14.4 MB before compression); analysis-only visitors do not download the model. Limits: 12 MiB per image, 24 megapixels and 12,000 pixels on either side. A working copy is downscaled to at most 1,600 pixels per side. Closing the importer releases its worker and temporary images. No image is saved in account or browser storage.
Analysis pauses during scanning and resumes afterwards. Reviewing or cancelling leaves the current game, history cursor, view and editor draft intact. Loading a confirmed valid position creates a new line; existing work requires replacement confirmation. An invalid draft can instead be corrected in the unlocked editor. Chess validation does not prove that the position matches the picture.
Model provenance and support limits · Licences
Privacy and advertising
The site includes Google AdSense (publisher ca-pub-6469944033866162). Google's scripts make network requests and may use cookies or similar technologies according to their settings and applicable consent choices. This is separate from the local chess engine. See Google's advertising privacy information. Standard hosting access logs may also record requests.
The analysis workspace is reserved for chess controls. Advertising settings and any required consent messages are managed by the site operator in AdSense. No ad approval or serving status is implied.