Free Sudoku Online

Sudoku in four levels

Play free Sudoku online in four levels: easy, medium, hard and expert. Easy is a gentle start for beginners, and expert will test seasoned solvers. Every puzzle has exactly one solution.

The numbers are large and clear, and there is no time limit. Pencil in notes, undo and redo, check for mistakes or ask for a hint. You can also print any puzzle with an answer key.

How to play

1. Choose a level and press Start.
2. Tap an empty square, then tap a number from 1 to 9.
3. Each row, each column and each of the nine 3×3 boxes must contain every number from 1 to 9 exactly once.
4. Use Notes to pencil in the numbers a square might be, then fill the whole grid to finish.

Tips

• Start with the number that already appears most often in the grid; it usually has the fewest places left to go.
• Look along a row of three boxes: if a number is in two of them, it must go in a particular row of the third.
• When a square can only hold one number, fill it in, then look again at its row, column and box.
• Use notes on harder puzzles. If two squares in a row can only be the same two numbers, those numbers cannot go anywhere else in that row.
• Never guess. Every puzzle here can be solved by reasoning alone.

Features

• Four levels: Easy, Medium, Hard and Expert
• Every puzzle has exactly one solution
• Notes (pencil marks), undo and redo
• Check marks wrong numbers in red, with no penalty to your time
• Hints that fill in one correct square
• Printable puzzles on US Letter or A4, with an optional answer key
• Your game and best time for each level are saved on your device

Questions and answers

What are the rules of Sudoku?

Fill the grid so that every row, every column and every 3×3 box contains the numbers 1 to 9, each exactly once. Some numbers are given at the start and cannot be changed.

Which level should a beginner choose?

Start with Easy. It gives 40 to 44 numbers and can be solved by finding the only place a number can go. Move up to Medium when Easy feels comfortable.

What makes a puzzle hard or expert?

Fewer numbers are given and the reasoning is deeper. Hard gives 28 to 31 numbers and needs ideas such as pairs and locked candidates. Expert gives 23 to 27 numbers and needs more advanced techniques.

Can I print the puzzles?

Yes. Press Print, choose the puzzle only or the puzzle with the answer key, and add a line for a name and date if you like. The puzzle fits on one page of US Letter or A4, and the answer key prints on a second page.

Does every puzzle have one solution?

Yes. Every puzzle is checked by computer to have exactly one solution, so you never need to guess.

Is there a timer?

There is no time limit. A timer counts quietly and pauses when you switch tabs. You see your time at the end, or you can turn on Show the timer while I play.