Play Sudoku Online

Sudoku is a number placement puzzle played on a 9×9 grid divided into nine 3×3 boxes. The puzzle starts with some cells already filled in. Your job is to complete the grid so that every row, every column, and every 3×3 box contains each digit from 1 to 9 exactly once. No arithmetic is involved — Sudoku is pure logic.

Every valid Sudoku puzzle has exactly one solution, reachable entirely through deduction. You never need to guess if you apply the right techniques. That guarantee is what gives the game its satisfying structure: every impasse is a clue that you have missed something, not evidence that the puzzle is unsolvable.

How to Play

Select an empty cell and enter a digit from 1 to 9. The digit must not already appear in the same row, the same column, or the same 3×3 box. Work through the grid cell by cell, using the filled digits to narrow down what each empty cell can possibly contain. When a cell can only hold one digit, fill it in. Use that new information to narrow down neighboring cells further.

Most implementations include pencil marks — small candidate numbers you can jot into a cell to track possibilities without committing to an answer. These become essential on harder puzzles.

Solving Techniques

Sudoku difficulty is defined by which techniques are required to reach the solution without guessing:

• Naked singles — a cell where only one digit remains possible after eliminating everything in its row, column, and box. This is the most basic technique and sufficient for easy puzzles.
• Hidden singles — a digit that can only go in one cell within a row, column, or box, even if that cell has multiple candidates. Spotting these clears the way on medium puzzles.
• Naked and hidden pairs/triples — groups of cells that share a locked set of candidates, allowing you to eliminate those candidates from other cells in the same unit. Required for hard puzzles.
• X-Wing and Swordfish — pattern-based eliminations that span multiple rows and columns, used in the most difficult puzzles.

Difficulty Levels

Sudoku puzzles are graded from easy to expert based on the techniques required. Easy puzzles are solvable with naked singles alone and are ideal for newcomers. Medium puzzles introduce hidden singles. Hard and expert puzzles require chaining multiple advanced techniques in sequence. The same 9×9 grid, four very different experiences.

Play Anywhere, No Setup Required

This version of Sudoku runs in your browser on any device. The grid is crisp and easy to use on both touchscreen and desktop, with support for pencil marks, undo, and mistake highlighting. No download or account needed — open the page and start solving.

Who Plays Sudoku?

Sudoku is one of the most popular logic puzzles in the world, published daily in newspapers and played by hundreds of millions of people. Logic puzzle fans, crossword solvers, and strategy game players all gravitate toward Sudoku for its clean rules and deep solving depth.

It is also widely used in educational settings to develop logical thinking and concentration. Completing a difficult Sudoku grid without any mistakes produces a distinctive sense of accomplishment that keeps players coming back for one more puzzle every day.