Free sudoku online: play, print or solve

Free sudoku to play, print or solve

This page gives you free sudoku puzzles at four levels: Easy, Medium, Hard and Expert. Every puzzle is new, has exactly one solution and carries a code such as 2-K7Q9XP, which opens the very same puzzle on any other device. You can also print puzzles and use the sudoku solver on a grid from a newspaper. Everything runs in your browser, with no account.

Sudoku rules

The grid has 81 cells: 9 rows, 9 columns and 9 boxes of 3 × 3. Fill it with the digits 1 to 9 so that every row, every column and every box contains each digit exactly once. The givens, shown in bold, never move. There is no arithmetic involved: nine colours would work just as well.

How to play

1. Pick a level under “New puzzle”.
2. Click a cell, then type a digit or tap the on-screen number pad. Arrow keys move around, Delete erases.
3. “Notes” (or the N key) adds small pencil marks. When you place a digit, it is removed from the notes in its row, column and box.
4. With “Show conflicts” ticked, two equal digits in the same row, column or box turn red. “Undo”, “Redo”, “Hint” (reveals one cell) and “Check” (crosses out wrong digits) complete the set.

The timer pauses when you switch tabs. Your game in progress and your statistics stay on your device, so you can close the page and carry on tomorrow.

Basic techniques, with an example

Candidates. If a row already holds 1, 2, 4, 5, 6, 7 and 9, its two empty cells can only take 3 or 8.

Naked single. If the column of the first of those cells already has an 8, that cell must be 3, and the other one is 8.

Hidden single. If two of the rows and two of the columns crossing a box already contain a 7, only one cell of the box is left for the 7, even if that cell could also take other digits.

Pairs. If two cells in a row only accept 2 and 6, those digits belong to them: cross 2 and 6 off the other seven cells. A cell that was torn between 2, 6 and 9 becomes a 9.

The four levels

Levels are measured, not guessed: before handing you a puzzle, the tool solves it with those techniques only. A Hard puzzle cannot be finished with singles alone, and an Expert one cannot be finished without trying a hypothesis.

Tips for beginners

• Start with the digit that appears most often: if six 4s are already in place, the last three are quick to find.
• Do not guess on easy puzzles: one wrong digit spoils everything that follows.
• Stuck? “Check” tells you whether a mistake has crept in without giving anything away.

A puzzle for the mind

Sudoku keeps your attention and logic busy for the length of a puzzle, and many players enjoy it as a quiet break in the day. It is a pastime, not a treatment: there is no solid evidence that it protects memory.

Printable sudoku for kids and seniors

Under “Printable sudoku”, choose the level, 1, 2, 4 or 6 puzzles per page, the number of pages and US Letter or A4, then tick “Add the answers on a separate page”. One puzzle per page gives large cells that are easy to read for a grandparent or an 8-year-old learning the game; six Easy puzzles per page make a handy booklet for a car journey.

Frequently asked questions

Does every puzzle have only one solution?

Yes. Each cell that is removed is checked: if the puzzle could then be solved in two ways, the digit goes back.

How do I share a puzzle?

Click “Copy link”, or give the code: typed into “Replay a puzzle from its code”, it opens exactly the same puzzle.

How do I solve a puzzle from a newspaper?

In “Sudoku solver”, copy the digits and click “Solve”. You get the solution, or a message saying there is none or more than one, which usually means a digit was mistyped.

Why did my best time not change?

Best times only count puzzles finished without a hint. The win is still added to your puzzles solved.