Privacy Policy
BlunderGym for Android · Effective 12 October 2026
BlunderGym imports your own chess games, finds your blunders with a chess engine that runs on your phone, and turns them into puzzles. It has no accounts, no ads and no analytics, and the developer receives no data from it.
What the app sends over the internet
When you add a Lichess or Chess.com username and import or sync games, the app asks that site's public game-export API for the games of that username. The request contains the username, the time range and time controls you chose, and an app identifier. Lichess and Chess.com handle these requests under their own privacy policies (Lichess, Chess.com). Nothing else leaves your phone, and nothing is sent to the developer.
What the app stores on your phone
- The usernames you entered and the games imported for them
- The puzzles found in those games, and your training history (which puzzles you solved or missed, and when)
- Your settings
The analysis runs on your phone with the Stockfish chess engine; your games are not uploaded anywhere for analysis. If Android backup or device transfer is on, Android may include this data in your backup according to your Google/Android settings.
Keeping and deleting your data
Your data stays on your phone until you delete it. In the app, Settings → Remove next to an account deletes that account's games, puzzles and history, and Settings → Delete imported games and puzzles deletes them all. Clearing the app's storage in Android settings, or uninstalling the app, deletes everything it stores.
Permissions
- Internet: to download your games from Lichess and Chess.com
- Notifications (optional): to show analysis progress while your games are analyzed
BlunderGym does not use your location, contacts, camera, microphone or files, has no sign-in and no in-app purchases, and does not sell or share personal data.
Children
BlunderGym is not directed at children and collects no personal data from anyone.
Changes
If this policy changes, the new version is published at this address with a new effective date.
Contact
BlunderGym is made by an independent developer. For privacy questions or requests, email chessodds.app+blundergym@gmail.com.