The Basic Rules

• Use only the numbers 1 through 9.
• Each number can appear only once in every row.
• Each number can appear only once in every column.
• Each number can appear only once in every 3×3 box.

Getting Started

A sudoku puzzle starts with some numbers already filled in. These are called "givens." A well-made puzzle has exactly one solution that can be reached through logic alone — you never need to guess.

Beginners should look for rows, columns, or boxes that are almost complete. If a row already has the numbers 1 through 8, the empty cell must be 9. That is the simplest form of solving.

Simple Solving Tips

• Scan for singles: Look for a number that is missing from a row, column, or box and can only go in one cell.
• Work box by box: Focus on one 3×3 box at a time instead of scanning the whole grid.
• Pencil in candidates: Write small notes of possible numbers in empty cells to spot patterns.
• Check rows and columns together: A number needed in a box might be blocked from some cells by the same number in a row or column.

Difficulty Levels

Our sudoku generator offers four difficulty levels. Easy puzzles have more givens and simple patterns, making them great for kids or first-time players. Medium and hard puzzles require more advanced techniques. Expert puzzles are designed for seasoned solvers who want a serious challenge.

Do you need math to solve sudoku?

No. Sudoku uses digits as symbols only — there is no adding or subtracting. Any nine distinct symbols would work just as well.

How do you solve hard sudoku puzzles?

Hard puzzles need candidate notes. Pencil the possible numbers into each empty cell, then look for pairs: if two cells in a unit can only hold the same two numbers, those numbers can be removed from every other cell in that unit.

Does every sudoku have only one solution?

A properly made puzzle has exactly one solution reachable by logic. Every puzzle from our generator is checked for a unique solution before it is printed.