Play Sudoku Online Free

Play sudoku online for free, right in your browser. Choose one of five levels, Easy, Medium, Hard, Expert or Hardest, and fill in the grid with a tap, a click or the keyboard. There are more than 8,000 puzzles, and every one has exactly one solution. From Easy to Expert you can always get there by logic alone, with no guessing. There is no sign-up and nothing to download, and the game works on a computer, a tablet or a phone.

Stuck on a square? Press Hint and the game fills it in and tells you why in one short sentence, such as “7 can only go here: it’s the only cell in the top-right box that can still hold a 7.” You also get pencil-mark notes, unlimited undo and a timer you can pause or hide. The numbers are big and bold, and Settings has a light, high-contrast theme. Your game saves itself as you play, so you can close the page and pick up where you left off.

How to Play Sudoku

A sudoku grid has 81 squares: nine rows, nine columns and nine 3×3 boxes, marked off by the thicker lines. Some squares already hold a number. Your job is to fill in every empty square with a number from 1 to 9 so that:

each row contains every number from 1 to 9 exactly once,
each column contains every number from 1 to 9 exactly once, and
each 3×3 box contains every number from 1 to 9 exactly once.

That is the whole rule. The numbers given at the start are part of the puzzle and cannot be changed. You never add anything up: the numbers are only symbols, and nine letters would work just as well. Every puzzle here has a single correct solution, and the puzzle is solved the moment the last square is filled in correctly.

Playing on this page

Fill in a square: tap or click it, then tap a number on the number pad (or type 1 to 9). The numbers you place are blue; the puzzle’s own numbers are black.
Number pad: each key shows how many of that number are still to place, and it greys out once all nine are on the board.
Highlights: the selected square’s row, column and box are shaded, and every square holding the same number lights up, so you can see at a glance where a number can still go.
Notes: turn on Notes to write small pencil marks, the numbers that might fit a square. When you place a number, it is removed from the notes in its row, column and box automatically.
Undo, Erase and Hint sit right by the board. Undo takes back as many moves as you like.
Pause: tap the timer to pause; the board is covered until you come back. The game also pauses by itself when you switch to another tab.
Settings (top right) holds your statistics, the in-game help, sound (off until you turn it on) and the options: mistakes, highlights, automatic note clearing, the timer and the theme.

Mistakes

A number that clashes with another, meaning the same number twice in a row, column or box, always turns red. Beyond that, you choose how strict the game is in Settings:

Off (the default): only clashes are shown. You find your own errors, as on paper.
Show wrong digits: any number that does not match the solution turns red at once.
3 mistakes and you lose: wrong numbers turn red and count against you; the third one ends the game. You can then try the same puzzle again or start a new one.

A change of this setting applies from your next game, so a game in progress keeps the rules it started with.

Keyboard shortcuts

1–9 place a number (the numeric keypad works too)
Arrow keys or W A S D move around the grid
Backspace, Delete or 0 erase
N turns notes on and off, H asks for a hint
Z or Ctrl/⌘+Z undoes, Space pauses and resumes

Sudoku Tips and Strategies

Every puzzle on this page can be cracked with a handful of patterns. Here they are in plain words, from the first one you will use to the one that Expert puzzles ask for.

Singles: start here

Pick a number, say 4, and look at one box. If every square in that box but one is ruled out, because a 4 already sits in its row or column, the 4 must go in the last free square. That is a hidden single. The other kind is a naked single: a square whose row, column and box already hold eight different numbers, so only the ninth can go there. Easy puzzles need nothing more.

Use notes

When the singles run out, turn on Notes and write the numbers that could still go in each empty square. The patterns below are all about these notes, and crossing a note out is how you make progress until a single appears again.

Pairs

If two squares in the same row, column or box can each hold only the same two numbers, say 3 and 7, then those two squares will take the 3 and the 7 between them. Cross 3 and 7 off every other square in that row, column or box: that is a naked pair. A hidden pair works the other way round: if two numbers can only go in the same two squares of a row, column or box, those squares cannot hold anything else, so clear their other notes. Triples follow the same idea with three squares and three numbers.

Pointing and claiming

Suppose that inside one box, all the places left for a 5 lie in the same row. The box’s 5 will be in that row, so no other square of that row, outside the box, can be a 5. That is pointing. Claiming is the reverse: if in a row (or column) all the places left for a 5 sit inside one box, then the 5 of that box must be in that row, and you can cross 5 off the box’s other squares.

X-Wing

Look for a number that has exactly two possible squares in each of two rows, with those squares in the same two columns, like the four corners of a rectangle. The number must take two opposite corners, whichever way round, so it fills both of those columns. Cross it off every other square in the two columns. The same works with columns and rows swapped. Swordfish is the same idea with three rows and three columns.

Not sure what to look for next? Press Hint: it names the technique it used and highlights the squares involved, which is a quick way to learn these patterns.

Difficulty Levels

Choose the level with the level menu next to the board. Each level is graded by the hardest technique a puzzle needs, not just by how many numbers are given:

Easy — 36 to 42 numbers given and singles only. A relaxing puzzle and a good way to learn.
Medium — fewer numbers given (about 29 on average). Some puzzles still need only singles but take more searching; the others need pointing, claiming or a naked pair.
Hard — needs a hidden pair or a naked or hidden triple somewhere along the way.
Expert — needs an advanced pattern: X-Wing, XY-Wing, Swordfish, XYZ-Wing, a quad or simple coloring.
Hardest — 50 puzzles with only 21 or 22 numbers given that stump every technique above. You will need long chains of reasoning or some trial and error, and here a hint may simply reveal a square.

Easy, Medium, Hard and Expert have 2,000 puzzles each, and you will not see the same puzzle twice until you have played them all. Settings → Statistics keeps your games played, win rate, best and average times and winning streak for every level.

Frequently Asked Questions

Is this sudoku free?

Yes. Every puzzle and every level is free to play, with nothing to buy, no sign-up, no account and no download. Open the page and play.

Does every puzzle have only one solution?

Yes. Each puzzle was checked by computer to have exactly one solution. Every puzzle from Easy to Expert can be solved by logic alone, without guessing.

What happens if I make a mistake?

By default nothing is judged: only a clash, the same number twice in a row, column or box, turns red. In Settings you can choose Show wrong digits, which marks any number that does not match the solution, or 3 mistakes and you lose. A change applies from your next game. Undo takes back any move.

How do hints work?

Press Hint and the game fills in one square and explains why in a short sentence, naming the technique and highlighting the squares it uses. If one of your numbers is wrong, the hint corrects that first. On the Hardest level, when no standard technique works, a hint reveals one square. You get up to 3 hints per game, at every level.

Can I play sudoku on my phone?

Yes. The board fills the screen of a phone, tablet or computer, with big numbers and a number pad under the board on a phone. Your game is saved as you play, so you can close the page and carry on later.

What is the hardest level?

Hardest: 50 puzzles with only 21 or 22 numbers given that defeat all the techniques the Expert level uses, including X-Wing and Swordfish. You will need long chains of reasoning or some trial and error.

Will I get the same puzzle twice?

Not until you have played every puzzle at that level: there are 2,000 each at Easy, Medium, Hard and Expert. The game remembers which ones you have played in this browser.

Does the game keep my best times?

Yes. Settings, then Statistics, shows for each level the games played and won, your win rate, best and average time and your winning streak. They are stored in your browser on this device.