Free Sudoku Online

How to play sudoku

Fill the grid so that every row, every column and every 3×3 box holds the digits 1 to 9 once each. Some digits are given at the start; you work out the rest by logic. You never need to guess: each puzzle here has a single solution that can be reached step by step.

Tap a square, then tap a number. Turn on Notes to pencil in candidates. On a keyboard, type 1–9, use the arrow keys to move, Backspace to erase, N for notes and Ctrl+Z to undo. Your game saves itself on this device, so you can close the tab and come back.

New to the game? Read how to play, then follow our step-by-step beginner walkthrough, which solves a whole puzzle in front of you and explains every digit.

Choose your level

How our levels are set

Many sites rate a puzzle by how many digits it starts with. That is a rough guide at best: a puzzle with few givens can be easy, and one with many can be hard. We grade each puzzle by solving it the way a person would and noting the hardest technique it needs.

• Easy falls to naked singles alone: there is always a square where only one digit fits.
• Medium needs at least one hidden single: a digit with only one possible square in a row, column or box.
• Hard needs locked candidates or naked pairs, which work on your notes rather than placing digits directly.
• Expert needs more than all of those, such as hidden pairs, X-Wings or XY-Wings.

If a newly made puzzle doesn't match the level you chose, it is set aside and another one is tried. Our guide on how sudoku puzzles are made walks through the whole process, from a blank grid to the puzzle on your screen.

What you get

• A fresh puzzle whenever you want one. Puzzles are generated in your browser, so there is no fixed list to run out of.
• Hints that teach. A hint fills one square and, where it can, names the technique that finds it with a link to how it works. If one of your digits is wrong, the hint points that out first.
• Your choice of help. Show mistakes marks wrong digits in red; turn it off if you'd rather find your own errors. Undo goes back up to 200 moves.
• A daily puzzle at every level, the same for everyone on the same date, and printable sheets with answer keys for paper solving.
• No account and no app. Your progress is kept in this browser only.

Learn as you go

Our guides take you from your first puzzle to expert patterns, with worked examples on real grids:

• Naked and hidden singles, the two ways every digit is eventually placed
• Pencil marks: notes that help instead of clutter
• Locked candidates and pairs for hard puzzles
• X-Wing, Swordfish and XY-Wing for expert puzzles
• Common mistakes and how to get unstuck

Prefer cages and sums? Try killer sudoku, with our killer strategies guide and the full cage combinations table.