Sudoku

Play Sudoku Online, Free

A clean 9×9 Sudoku board with four difficulty levels, pencil notes, undo, three hints and a pause button. Nothing to install, no account to create — your puzzle is generated on your own device and saved there if you close the tab.

What you are looking at

Sudoku is a logic puzzle played on a grid of 81 squares, divided into nine boxes of nine squares each. Some squares start with a digit already in them — these are the clues or givens. Your job is to fill every remaining square so that each row, each column and each 3×3 box contains the digits 1 to 9 exactly once.

That single rule is the whole game. There is no arithmetic involved, and the digits could just as easily be nine colours or nine symbols — what matters is that they are nine distinct things that cannot repeat within a row, column or box. Every puzzle on this site has exactly one solution, and every one of them can be reached by pure deduction. You never need to guess.

The controls, briefly

  • Select a square by clicking or tapping it, then type a digit or tap the number pad. Typing the same digit again clears it.
  • Notes (the pencil button, or the N key) switches the pad into candidate mode, so digits go into the corner of a square as small pencil marks instead of committing an answer.
  • Hints reveal the correct digit in the selected square. You get three per puzzle, and each one costs points at the end.
  • Pause (the pause button next to the clock, or the P key) stops the timer and blurs the board so you can step away without losing your place. The game also pauses itself if you switch to another tab.
  • Undo steps back through your moves, including mistakes. Arrow keys move the selection; Backspace erases.

Choosing a difficulty

The four levels differ in how many clues you start with and, more importantly, in which techniques the puzzle demands. Easy puzzles fall to simple scanning: somewhere on the board there is always a square with only one possible digit, sitting in plain sight. Medium puzzles start hiding those squares, so you need to work box by box rather than square by square — the deduction that reopens them is the hidden single.

Hard puzzles reach a point where no single square can be resolved on its own and you have to reason about naked pairs — two squares in a row that between them must hold a 4 and a 7, which rules a 4 and a 7 out of every other square in that row. Expert puzzles add another layer on top of that, where the useful deduction — the X-Wing — spans two rows and two columns at once.

Each level has its own page, with the board set to that difficulty and a walkthrough of the techniques it demands: easy Sudoku, medium Sudoku, hard Sudoku and expert Sudoku. Or read the level guides side by side on the how to play page.

If a level feels impossible rather than merely hard, that is usually a sign you are missing one specific technique rather than that you are bad at the puzzle. The solving techniques guide walks through each one in the order you actually need them.

How scoring works

You earn 10 points for every square you fill in correctly yourself. When you finish, a completion bonus is added based on the difficulty, plus a speed bonus for every second you beat the par time for that level. Mistakes cost 50 points each and hints cost 75, which is why a careful slow solve often beats a fast messy one.

Finish a puzzle and you can post the result to the daily and weekly leaderboards with nothing but a nickname — no email, no password, no account. Boards reset at midnight UTC and on Monday morning UTC respectively, so there is always a fresh one to climb.

Away from the board

Stuck on a grid from a newspaper or another app? The Sudoku solver takes the clues from any 9×9 puzzle and returns the answer, along with whether that puzzle has one solution, none at all, or more than one — which is often the real explanation for a grid that refuses to work out.

Playing with a child, or starting from nothing yourself? The small boards on the Sudoku for kids page use the same rule on a 4×4 or 6×6 grid, which takes a minute or two rather than twenty and is the quickest way to see how the puzzle works.

Prefer paper? The printable Sudoku sheets generate fresh puzzles at any of the four levels, one, two, four or six to a page, with an optional answer sheet on a separate page.

New to Sudoku?

Start with the rules and a worked example. It takes about five minutes to read and covers everything you need for the easy and medium levels. The FAQ answers the questions that come up next, including the one everybody asks: no, a well-formed Sudoku never requires guessing.