Sudoku - Play Online with New Puzzles

Sudoku presents a 9×9 grid where each row, column, and 3×3 box must contain digits 1 through 9 without repetition. Choose difficulty, play the generated puzzle in the grid, and check entries against rules. New puzzles build a complete grid, remove clues while preserving a single solution, and verify solvability before display.

Play sudoku online

Clue cells arrive fixed and greyed; open cells accept digits 1 through 9 from the keyboard or on-screen focus. New puzzle replaces the grid at the chosen difficulty. Check compares filled cells against sudoku placement rules and the stored solution, reporting conflicts when a digit breaks a row, column, box, or answer key.

The layout includes Clear entries to wipe player input while keeping clues, plus Undo in the control row for stepping back recent edits when enabled in the build. A simple timer display tracks elapsed time in the tab. Pencil marks, hints, and automatic candidate lists are not on this page yet; solving stays pencil-and-paper logic in your head or on paper beside the screen.

Learn the rules of sudoku

The grid has eighty-one cells arranged in nine rows, nine columns, and nine three-by-three boxes outlined by thicker borders. Digits 1 through 9 must appear exactly once in each row, once in each column, and once in each box. Clues given at start cannot be changed.

Guessing is not required on well-formed puzzles. Every step should follow from eliminations until only one digit fits a cell. A puzzle with multiple solutions violates standard newspaper rules; this site rejects those grids at generation time.

Solve with naked and hidden singles

A naked single is a cell whose candidates collapse to one digit after you eliminate values already present in its row, column, and box. A hidden single is a digit that can occupy only one cell within a row, column, or box even if that cell still lists other candidates on paper.

Easy puzzles on this site often fall quickly to repeated single finding. Mark candidates on paper if the on-screen grid lacks pencil marks. Each placement should propagate eliminations to neighbouring cells.

Solve with pairs and pointing pairs

A naked pair is two cells in a unit that share the same two candidates; other cells in that unit lose those candidates. Hidden pairs compress two digits to two cells inside a unit.

Pointing pairs link a box and a line: if a digit’s candidates in a box lie on one row, that digit can leave the rest of that row outside the box.

Harder presets assume you may need these steps after singles stall. The browser tool does not highlight pairs automatically; the sections below teach the methods while you play manually. Advanced tactics such as X-wing are outside this brief guide.

Understand how difficulty is rated

Difficulty here reflects which techniques remain necessary after generation, not raw clue count alone. Easy boards yield to singles with few cross-box steps. Medium boards introduce tighter candidate patterns. Hard boards expect pair-style logic before the grid breaks open. Selecting easy, medium, or hard before New puzzle adjusts how aggressively clues are removed while keeping a unique solution.

A hard puzzle with many clues can still be hard if the required logic is deep.

Understand how these puzzles are generated

The engine first completes a valid full grid with backtracking and shuffle, then removes clues while a solver counts solutions. Removal stops when only one solution remains or when the difficulty target is met. Grids with zero or multiple solutions are discarded before you see them.

That process mirrors common programmatic sudoku construction. Uniqueness is verified before publish, so Check can compare against a single stored answer. Regenerating always draws a new shuffle path, so two medium clicks are unrelated boards.

FAQ

Closing summary

Sudoku on this site offers generated 9×9 puzzles with verified unique solutions, three difficulty presets, in-browser entry, check against rules and answer, and editorial notes on singles and pairs below the play area. Advanced UI aids may arrive later; logic-first solving matches pen-and-paper sudoku today.