Before scanning#
Use a well-lit, in-focus image with the complete Sudoku grid visible. Keep the phone parallel to the page or screen, avoid glare and heavy shadows, and make sure printed or handwritten digits are distinct from the grid lines.
Camera import is a convenience for recognising a puzzle, not a substitute for reviewing it. Do not begin solving until the recognised grid matches the source puzzle.
Review the recognised grid#
After scanning:
- Check that every given digit is in the correct row and column.
- Correct cells that were missed or misread.
- Confirm that the puzzle has a valid starting grid.
- Save the puzzle only after the review is complete.
If the scan is unreliable, crop closer to the grid, improve the lighting, remove reflections, or enter the puzzle manually using Creating and importing puzzles.
Camera permissions#
Lab Sudoku needs camera access only when you choose the scan workflow. Grant the permission when you want to scan, and review your Android permission settings if scanning stops working. You can continue using manual entry and regular puzzles without camera access.
Images and privacy#
The scanner and Sudoku digit recognition run through Google Play services and on-device processing. Lab Sudoku receives the recognised puzzle and stores a temporary board preview in its app cache for the review workflow; the feature does not intentionally upload the source puzzle image to Lunar Hut.
Only use images you are comfortable processing through the scanner. Avoid including personal documents or unrelated content in the frame. Review the current permission prompt and the Lab Sudoku Privacy Policy for the authoritative description of app data and third-party services.
If you are reporting a recognition problem, send a redacted example only when necessary. Remove names, account details, or other unrelated personal information first.
Common problems#
The camera does not open#
Check that another app is not using the camera, confirm that Lab Sudoku has camera permission, and restart the app. If the device still blocks access, use manual entry while investigating the Android permission state.
Digits are recognised incorrectly#
Retake the image with better light, less perspective distortion, and the whole grid in frame. Review and correct every cell before saving.
The puzzle is rejected as invalid#
Look for a duplicated digit in a row, column, or box, or a digit that was entered in the wrong cell. Correct the grid or start again with manual entry.