Support

Open Play and choose Easy, Medium, Hard or Master. A new board is generated on your device. To play a puzzle from a book or another app, choose Import a puzzle and paste its 81 digits, using 0 or . for empty cells.

No. SudokuLab has no account. Your progress is saved on the device and browser you are using.

A level is what the puzzle demands, not how empty it looks. Easy needs singles only. Medium also needs locked candidates, pairs or triples. Hard needs one or two advanced moves. Master needs more of them, or a long one such as a Swordfish, an X- or XY-Chain, or an alternating inference chain.

Yes. While SudokuLab is open in a supported browser, use the browser’s Install or Add to Home Screen option. The installed app keeps working offline.

Tap a cell to select it, then tap a number on the pad or type it on your keyboard. Use the arrow keys to move, and 0 or Backspace to erase.

Turn on Notes, or press M, to write candidates as pencil marks instead of answers. Fill candidates writes every candidate for you. With Auto-remove notes on (Settings → Board), placing a digit clears it from its peers’ pencil marks.

Yes. Undo and Redo sit beside Notes under the board. On a keyboard, use ⌘/Ctrl-Z and ⌘/Ctrl-Shift-Z.

The selected cell is filled with the accent colour, its row and column are banded, and every cell already holding that digit is ringed, so you can see where the number is blocked. You can change these in Settings → Board.

Hint opens the coach on the easiest useful step on your board. It shows the pattern cells first, then the reasoning in plain language, then the elimination. Stop at any stage.

No. A hint shows one step, never the solution. Explain step by step plays that one move on your grid, with your cells and your digits.

Yes. Choose a family under Look for, such as Fish, Wings or Chains, and Hint will look for that instead of the best move.

Turn off Stepped hints in Settings → Coach.

Learn takes one technique at a time in three steps. Learn plays it on a worked example. Practise puts you on a taught position, or a fresh variation of it. Challenge generates a complete Sudoku for practising it.

A Focused board can be finished with the technique and the ones taught before it; one solving path using only those was checked to the end. A Mixed board practises the technique the same way, then may need other techniques, which it lists before you start. Neither promises the technique is the only way through.

Wrong final digits are refused, and each counts as one mistake. Three mistakes end the Challenge. Pencil marks are never counted as mistakes.

No. Your Play board and your Challenge are kept apart, and each tab offers its own Continue.

A short quiz of five unseen positions with the technique hidden. Name the technique you can see, then make the move it justifies. Using Hint or Explain marks that answer as assisted.

Yes, once it has loaded. Boards are generated on your device, so you can play and learn without a connection.

The web app downloads updates from its host when you are online. When a new version is ready, SudokuLab shows a notice with Update now. The build you are running is shown on About (Settings → About).

In the browser’s local storage on this device, or in the bundled app’s storage. It is not uploaded, and it does not sync between devices or browsers.

Local progress is removed when this site’s browser data is cleared, or when the app’s data is cleared or it is uninstalled. Progress in one browser or device does not appear in another. If you exported a backup, you can restore it.

Yes, but each keeps its own progress. To carry progress over, export a backup on one and restore it on the other.

In the web app, open Settings → Backup and transfer and choose Export backup. Keep the file somewhere safe.

One file with your Play and Challenge games (with their marks and mistakes), Learn progress, practice results, stats and settings. It may contain your entire puzzle and progress history, so share it only deliberately.

Not yet. The bundled iOS and Android proof builds can restore a backup file you select, but do not currently offer export.

Open Settings → Backup and transfer, choose Restore from backup…, and pick the file. SudokuLab shows what the backup will replace before anything changes. Choose Replace my progress to continue.

Yes. Your current progress is kept as a recovery copy, and Settings offers Undo the last restore.

Email info@alosha.dev with your device and operating system, web app or bundled app, the build shown on About, which step failed, and whether the progress is still visible on the original device. Do not send the backup file unless you deliberately choose to share it.