Internetsudoku.net is a free online sudoku site — play instantly in your browser with no account and no download required. Pick from five difficulty levels, take on the daily challenge, or sharpen your skills with our strategy guides.

What is sudoku?

Sudoku is a logic puzzle — not a maths test. The grid is 9×9, divided into nine 3×3 boxes. Your goal is to fill every row, column, and box with the digits 1 through 9, using each digit exactly once in each unit.

When you start a puzzle, some squares are already filled in. These are called the givens — the starting clues from which you work out the rest. They cannot be changed. The fewer givens a puzzle has, the harder it tends to be, but placement matters as much as quantity.

Your task is to fill in the empty squares without repeating any digit in the same row, column, or box. Think of the puzzle as something that was once complete and then partially erased: your job is to restore it, one logical deduction at a time.

The key insight is that every solved square creates new constraints. If the digit 7 already appears in a row and a column, it can only go in one specific cell in the 3×3 box they share. Work through those constraints systematically — every puzzle has exactly one solution, and no guessing is required.

Difficulty is set by how many givens the puzzle contains and how they are arranged. A beginner puzzle might start with 36–40 filled cells; an extreme puzzle may have fewer than 25. The logic is the same at every level — only the number of deductions between you and the solution changes.

Sudoku Tips

The best way to learn sudoku is to play it. Start at beginner level and notice how the board opens up as you fill in cells. Scanning — working through rows, columns, and boxes to find digits that can only go in one place — is the technique most people pick up first. Ready to go further? Get more sudoku tips and hints →

The History of Sudoku

The history of Sudoku is an intriguing subject to those interested in the game. Based on its name, “Sudoku,” people would think that the game originated from Japan. However, this puzzle game was seen first in UK and the United States before it reached Japan. This game was first published by the Dell Magazine in New York in North America in late 1970s. Dell Magazine specializes in logic and puzzles and has published the game in their magazine with the name “Number Place". Read more about the history of sudoku →

Five difficulty levels — find your level

All five difficulty levels at internetsudoku.net are free to play directly in your browser — no account, no download, no paywall. Start with beginner sudoku puzzles if you have never played before, work up through easy and medium when you want more of a challenge, or try extreme sudoku puzzles when you are ready for the toughest grids. Want a new puzzle every day? The daily sudoku puzzle gives you a fresh grid each day and lets you track your solving streak week by week.

More about sudoku

You can read more about sudoku on Wikipedia. Go to wikipedia →

Easy Sudoku for Beginners

New to the game? Web sudoku easy is the best place to start. Our easiest grids come with more pre-filled cells, so every puzzle is solvable through simple logic — no guessing, no frustration. Once you are comfortable, move up through the five difficulty levels. Try easy sudoku →

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