Strictly Sudoku - A Free Sudoku Online

How to play

The sudoku grid consists of eighty-one squares in a nine by nine grid. To solve the sudoku, each square in the grid must contain a number between one and nine, with the following conditions:

• Each row of nine cells must contain each of the numbers from 1 to 9 once and only once.
• Each column of nine cells must contain each of the numbers from 1 to 9 once and only once.
• Each of the nine 3 by 3 boxes of nine cells must contain each of the numbers from 1 to 9 once and only once.

The sudoku starts with a partially filled grid and you must complete the grid while following the rules above. If you complete the grid, you've solved the sudoku.

Each sudoku on this site has one and only one unique solution.

Write notes with a pencil

Some people like to write small pencil numbers in each cell to indicate what numbers are possible in that cell. If you fill all the cells with their possible values, the answer may quickly become apparent. Particularly if some cells only have one possible value. Such cells are called an "Open Single"

Sudoku tips and tricks

There are a number of techniques for solving sudoku. They vary in complexity and ease of application but all have one thing in common - they aim to narrow the range of possible values in one or more of the cells in the sudoku. If, by applying the rules of sudoku, we can reduce the possible values in an empty cell to just one, we can enter that value in the cell, confident in the knowledge that it is correct.

The most common of these techniques are described on this website (under the grid when you select a difficulty). If you're new to sudoku, take a look at the beginners techniques then try some of our easy sudoku. More techniques for advanced players will be presented here soon.