About OneStop Sudoku

A place to explore Sudoku

OneStop Sudoku is an independent puzzle project that brings familiar Sudoku and a collection of variants into one place. Play a short 6×6 puzzle, settle into a classic grid, or learn a rule that changes the way you look at the board.

The browser game is free to play and does not require an account. Each mode offers Beginner, Easy, Medium, Hard, and Expert levels, with notes, three hints per puzzle, a timer, and personal high scores. You can keep an unfinished puzzle in every mode and difficulty.

Fifteen modes, different ways to think

Most modes use a 9×9 grid: place 1–9 once in each row, column, and 3×3 box, then apply the mode’s extra rule. Jigsaw changes the regions, and Mini uses a smaller grid. The rule shown with each game explains its markings.

Start with the grid

• Classic Sudoku focuses on rows, columns, and 3×3 boxes. It is a useful starting point for learning elimination and pencil notes.
• Jigsaw Sudoku replaces the square boxes with outlined, irregular nine-cell regions. Follow those boundaries when checking where a digit can go.
• Mini Sudoku uses 1–6 on a 6×6 board with 2×3 boxes. The smaller grid gives you fewer cells to track, while still offering all five difficulty levels.

Use sums

• Killer Sudoku adds dashed cages whose digits total the small number in the corner. A digit cannot repeat inside a cage.
• Arrow Sudoku asks you to make the digits along an arrow add up to the digit in its circle. Digits on the arrow may repeat if ordinary Sudoku rules allow it.
• Sandwich Sudoku places sums outside the grid. Each clue totals the digits strictly between 1 and 9 in its row or column; a zero means 1 and 9 are adjacent.

Look beyond the usual neighbors

• Diagonal Sudoku, also called Sudoku X, requires 1–9 without repeats on each of the two marked main diagonals.
• Hyper Sudoku, also called Windoku, adds four shaded 3×3 regions. Each of these also needs 1–9 without repeats.
• Anti-Knight Sudoku prevents equal digits from sitting a chess knight’s move apart: two cells in one direction, then one sideways.
• Anti-King Sudoku prevents equal digits from touching diagonally, including across box boundaries.

Read lines and symbols

• Thermo Sudoku has thermometers whose digits strictly increase from the round bulb. The digits do not have to be consecutive.
• Kropki Sudoku uses white dots for consecutive digits and black dots when one digit is twice the other. Not all possible dots are shown, so an unmarked pair adds no restriction.
• Renban Sudoku uses purple lines containing a set of consecutive, nonrepeating digits in any order.
• German Whispers uses green lines whose neighboring digits differ by at least five. More distant digits on the same line can repeat when the other rules allow it.
• Even/Odd Sudoku marks odd digits with shaded circles and even digits with shaded squares. Unmarked cells can contain either.

How the puzzles are made

New puzzles are generated in your browser. Before presenting a puzzle, the generator checks that its completed grid follows the selected mode’s rules and that the starting clues have exactly one solution under those rules.

Difficulty is assessed automatically using the deductions needed by the built-in solver, including singles, candidate eliminations, pairs, and, for some harder puzzles, contradiction deductions. These are the game’s own ratings, not individual human reviews. The same level can feel different across modes, especially while you are learning a new rule.

Creating a puzzle may take a moment. If the generator cannot finish its checks within its search limit, it asks you to try again. An unsuccessful attempt does not replace your existing saved puzzle.

Your own pace and progress

Notes let you record possibilities before committing to an answer. Pause when you need a break, turn on Night Mode, or adjust automatic cell selection and related-cell highlighting in Settings.

Puzzles, notes, scores, streaks, and settings are stored in this browser on this device. They do not sync between browsers, devices, or the iPhone app. Clearing the site’s browser data removes those saves. Read the privacy policy for details about information handled by the website.

Questions and feedback

The Help & FAQ explains controls, scoring, saved games, and common problems. For support or feedback, email onestopapps.support@gmail.com. If something goes wrong, include the mode, difficulty, browser, and what you were doing so the issue is easier to investigate.