ONESTOP SUDOKU
Help & frequently asked questions
Get comfortable with the controls, keep your place, and find your next deduction.
Play your first puzzle
- Choose a mode and difficulty. Classic Sudoku at Beginner is a useful place to learn the basic rules; Mini offers a smaller 6×6 board.
- Select an empty cell, then choose a digit on the number pad or type it on your keyboard. Starting clues are fixed and cannot be changed.
- Fill every row, column, and region without repeating a digit. Classic uses 1–9 and 3×3 boxes; Mini uses 1–6 and 2×3 boxes. In Jigsaw, follow the outlined irregular regions instead of square boxes.
- For a variant, read its rule before entering answers. Open the question-mark button above the board or expand “Rules & keyboard shortcuts” below it.
- Use Notes for possibilities and Hint when you want a cell revealed. Pause to stop the timer, or use the back arrow to save and return to the difficulty choices.
You have three hints and a limit of three mistakes in each puzzle. There is no countdown or time limit, so take the time you need to reason through an entry.
Controls and settings
On a phone or tablet, tap a cell and then a number. On a computer, you can use the same buttons or these keyboard shortcuts while a puzzle is active:
- 1–9: enter a digit, or toggle a pencil note when Notes is on. Mini accepts 1–6.
- ↑ ↓ ← →: move the selected cell.
- N: turn Notes on or off.
- H: use a hint.
- Backspace or Delete: erase your entry or notes in the selected cell.
- Ctrl + Z, or ⌘ + Z on Mac: undo a previous move.
Shortcuts are inactive while the game is paused or a dialog is open. To replace a number you entered, erase it first. Once every copy of a digit is correctly placed, its number-pad button is disabled.
Settings includes Night Mode, “Move to next empty cell,” and “Highlight related cells.” Automatic movement advances after a correct answer or a hint. Turn it off if you prefer to keep your selection in place.
Answers, notes, and hints
How do pencil notes work?
Select an empty cell, turn Notes on, then choose the digits you want to remember as possibilities. Choosing a noted digit again removes that note. Turn Notes off before entering your final answer.
Notes do not count as mistakes and do not earn points. They are your working possibilities, not a guarantee that a digit is correct. When you place a correct answer or use a hint, the game removes notes it can rule out from other cells using the puzzle’s constraints.
Why was an answer marked wrong when it did not repeat a number?
The game checks an entered answer against the puzzle’s unique completed solution. A digit may fit the visible row, column, and region at the moment but still make the puzzle impossible to finish. It counts as a mistake if it is not the solution for that cell.
The incorrect digit is not left on the board. After three mistakes the puzzle ends; you can start another puzzle or choose a different challenge. Use Notes when you want to record an uncertain candidate without making an answer attempt.
What does a hint do?
Each puzzle starts with three hints. Hint reveals the correct digit in your selected empty cell. If the selected cell is already filled, it reveals the first empty cell instead. A hint supplies an answer; it does not give a step-by-step solving explanation.
Revealed cells earn no points. Erasing or undoing a revealed digit does not make that cell eligible for points, and a spent hint is not returned.
What can Undo and Erase change?
Erase clears your answer or all notes in the selected cell. Undo steps back through recent entries, note changes, erasures, and revealed digits. Neither tool changes the original clues.
Undo can restore an earlier board and score, but mistakes and spent hints are permanent for that puzzle. The game keeps up to 60 recent moves for undo. Undo is unavailable after a puzzle has ended.
Scores, time, and daily streaks
How are points earned?
Correct answers you place earn points. The base amount increases with difficulty, and additional points reward a short interval since your previous scoring answer and finishing a row, column, or region. A move can complete more than one of those at once.
Notes and hints earn no points. Erasing a scored answer and entering it again does not award another set of points. Your best score for that mode and difficulty is updated when you complete a puzzle and beat your previous best.
Does pausing affect my time?
The timer runs during active play and stops while the game is paused or a game dialog is open. The game also pauses when the page becomes hidden, such as when you switch browser tabs. Resume the puzzle when you return.
There is no deadline to solve a puzzle. The timer records your active session, and quicker consecutive correct entries can earn pace bonuses.
How does the day streak work?
Complete at least one puzzle on consecutive calendar days to build a streak. The game uses your device’s local date. Solving several puzzles on the same day increases your solved count but adds only one day to the streak.
Completed puzzles and the day streak are shared across all modes. High scores are kept separately for each mode and difficulty. If you miss a calendar day, your next completion begins a new streak.
Saved games and browser access
Where is my progress saved?
The website automatically saves progress in this browser’s local storage. Each combination of mode and difficulty has its own unfinished puzzle, so you can switch challenges and return later. Choose that mode and difficulty again to continue.
There is no account or cloud synchronization. A different browser, browser profile, device, or the iPhone app has separate progress. Clearing this site’s browser data removes its games, notes, scores, streaks, and settings. Private browsing may discard those saves when the private session ends.
If the game reports that browser storage is unavailable or full, you can still play, but progress may not be saved. See the privacy policy for more about local storage.
Will starting a new puzzle delete my other games?
A new puzzle replaces only the unfinished save for its own mode and difficulty. Other combinations keep their saves. For example, a new Easy Classic puzzle replaces your Easy Classic game, while your Hard Classic and Easy Killer games remain available.
Switching to another mode or difficulty saves the current puzzle and resumes an unfinished game there if one exists. Completed and failed puzzles are not kept as resumable games.
Can I play offline?
The website needs a connection to load. Puzzle generation and play run in your browser, so an already loaded game can continue if the connection drops. However, the website does not provide a guaranteed offline installation: refreshing, reopening the page, or having the browser unload it may require a connection again.
Saved progress is local to the browser; being saved does not guarantee that the website itself will be available offline.
Why is a new puzzle taking time to appear?
The generator creates a board, checks that it has one solution, and evaluates its difficulty. Some combinations need more searching than others, and generation speed depends on your device.
You can cancel generation. If a search-limit or interruption message appears, choose Try again. Your existing saved game is not replaced unless a new puzzle is successfully created. If generation repeatedly fails, try an up-to-date browser and include the mode and difficulty when contacting support.
A few solving habits worth practicing
Start with a row, column, or region that has only a few empty cells. List its missing digits, then check the intersecting rows and columns. A cell with one remaining possibility is a single. Also look for a digit that has only one available position in an entire row, column, or region, even if that cell has several notes.
Use the variant’s rule alongside those basics. In Killer Sudoku, a two-cell cage totaling 3 must contain 1 and 2. On a thermometer, leave enough room for larger digits toward the tip. In Jigsaw, trace the region boundary carefully before ruling a digit out.
Do not infer rules from absent markings. An unmarked Kropki pair may still be consecutive or in a 1:2 ratio; an unmarked Even/Odd cell may have either parity; a row or column without a Sandwich sum has no extra sum restriction. The mode overview explains all fifteen variations.
When learning a variant, lower the difficulty and focus on one rule at a time. The levels are automatic ratings from the game’s solver, so a familiar mode and a new one may feel different at the same setting.
Need more help?
Email onestopapps.support@gmail.com with the mode, difficulty, browser and device, plus a description of what happened. A screenshot of the board or error can help explain a problem. Avoid including personal information you do not want to share.