What is Sudoku?
Sudoku is a logic puzzle played on a nine-by-nine grid divided into nine smaller three-by-three boxes. When you start, some squares already hold numbers. Your job is to fill every empty square so that each row, each column, and each three-by-three box contains the digits 1 through 9 exactly once. There is no arithmetic and no guessing is required — a well-made Sudoku always has a single answer you can reach through reasoning alone.
The modern version of the game took shape in the late 1970s and became a worldwide pastime in the mid-2000s, when newspapers began printing a daily grid. Today most people play on a phone or in a browser, which is where vSudoku comes in: open the page, and a new puzzle is waiting.
Six difficulty levels
We generate puzzles at six levels so there is always something that fits your mood and experience. The difference between them is how many numbers you start with and how much logical chaining you need to finish.
- Easy — plenty of clues and a gentle solving path. Ideal for learning or a relaxed break.
- Medium — a balanced challenge that rewards careful scanning.
- Hard — fewer clues, so you will lean on notes to track candidates.
- Expert — demands consistent use of intermediate techniques.
- Master — long chains of deduction and very little room for error.
- Evil — our toughest board, for solvers who want a real fight.
Features that make solving easier
Pencil notes
Jot candidate numbers in a cell before you commit, just like on paper.
Smart highlighting
Tap any number to light up every matching cell and its row, column and box.
Unlimited undo
Step back through your moves whenever you change your mind.
Hints when stuck
Reveal the correct number for a chosen cell to get unstuck without quitting.
Built-in timer
Track how long each solve takes and try to beat your own record.
Works everywhere
The board scales to any screen and runs entirely in your browser.
Why playing Sudoku is good for you
Sudoku is a low-stakes way to keep your mind active. Because the puzzle rewards patient, step-by-step reasoning, it gives your working memory and concentration a regular, gentle workout. Many players find the focused quiet of a solve genuinely relaxing — it is one of the few screen activities that asks you to slow down rather than speed up. It is suitable for every age, needs no special knowledge, and you can stop and pick it up again whenever you like.
How to get started
Choose a level above, then click an empty square and type a number, or use the on-screen keypad. If you are brand new, start with an Easy board and read our step-by-step guide to playing Sudoku. Once you are comfortable, our tips and strategy page walks through the techniques that unlock the harder levels. Want the formal rules? They are laid out on the Sudoku rules page, and our blog covers the history of the puzzle, its many variants, and advanced solving methods.