The Sealed Move app has a chess engine inside: Stockfish 11, compiled right into the app so every move you play is checked on your device, offline, for free. Stockfish is licensed under the GNU General Public License v3, and we honor that the way it's meant to be honored: the app that links it is open source under the same license.

Get the source

The complete corresponding source for the Sealed Move app (the iOS client and the coaching engine it links) is published at:

github.com/tjameswilliams/sealedmove-app

Each App Store release is tagged with its version number, so the source for the exact build on your phone is a tag away. If anything is missing or won't build, tell us and we'll fix it.

Credits

Stockfish: the Stockfish developers (see the AUTHORS file), GPLv3. The strongest thing in the app, and it isn't close.

The Pro Coach service, this website, and the Sealed Move name and brand are not part of the open-source release.