Free Sudoku
Play free sudoku online in four levels with notes, hints, undo and a daily puzzle, or print up to 20 unique puzzles as a PDF with an answer key.
Loading tool…
How to play and print sudoku
Sudoku is a 9 by 9 grid split into nine 3 by 3 boxes. Some cells already hold digits; your job is to fill the rest so that every row, every column and every box contains the digits 1 to 9 exactly once. No arithmetic is needed, only logic. Every puzzle here is generated on your device and checked to have exactly one solution.
- Choose a level: Easy, Medium, Hard or Expert, or press Daily puzzle for the puzzle of the day.
- Tap a cell, then tap a digit on the number pad or type 1 to 9. Use the arrow keys or WASD to move around the grid.
- Turn on Notes (or press N) to pencil in the digits a cell could still hold. Placing a digit clears that digit from the notes in its row, column and box.
- Use Undo and Redo as often as you like. Hint fills in one cell that can be worked out next, and mistakes are highlighted in red unless you switch that off.
- To print, choose 1, 2 or 4 puzzles per page and up to 5 pages, pick US Letter or A4 and download the PDF with its answer key.
How the puzzles are made and graded
Each puzzle starts as a random complete grid. Digits are then removed in pairs placed symmetrically around the centre, and after every removal a solver checks that only one solution remains. The puzzle is then solved again with human techniques to decide its level, and the level is the hardest technique the puzzle needs.
The puzzle number in the link (?seed=) and the level together recreate exactly the same grid, which is how the daily puzzle, shared links and printing all match what you see on screen.
What each level asks of you
The table shows the usual number of given digits and the techniques each level needs. Expert puzzles go beyond X-wings and can take a long time; they are meant for experienced solvers.
| Level | Given digits | Techniques needed |
|---|---|---|
| Easy | About 34–40 | Singles only |
| Medium | About 30–35 | Singles and locked candidates |
| Hard | About 26–31 | Naked and hidden pairs and triples |
| Expert | About 22–28 | X-wing or longer chains of reasoning |
Useful tips and limitations
- Start with the digit that already appears most often: the number pad shows how many of each digit are left to place.
- Look for a cell where only one digit fits, then for a digit that has only one possible cell in a row, column or box. Those two moves solve every Easy puzzle.
- On paper, print 4 puzzles per page for a compact booklet, or 1 per page for large, easy-to-read grids.
Common questions
Does every sudoku have only one solution?
Yes. After digits are removed, a solver counts the solutions and keeps the puzzle only if there is exactly one. You never need to guess between two valid answers.
What does the daily puzzle mean?
The daily puzzle is made from today's date on your device, so everyone who opens it on the same day gets the same grid at the chosen level.
Can I play sudoku without a mouse?
Yes. Move with the arrow keys or WASD, type 1 to 9, press Backspace to clear, N for notes, H for a hint and U or Z to undo.
Why is the expert level so hard?
Expert puzzles need at least an X-wing, and many need even longer chains of reasoning or trial and error. Use notes and expect to spend much longer than on a hard puzzle.
Every puzzle is made and played in your browser. Best times, scores and solved puzzles are saved only in this browser on this device; nothing is uploaded and no account is needed. Clearing site data removes them.