😊 Beginner's Guide to Sudoku

Never played Sudoku before? This guide will take you from zero to solving your first puzzle — step by step, no experience needed.

The three rules of Sudoku

Sudoku has exactly three rules. Every puzzle, every grid size follows them:

Every row must contain each number from 1 to 9 exactly once.
Every column must contain each number from 1 to 9 exactly once.
Every box (the 3×3 sections) must contain each number from 1 to 9 exactly once.

That's it. No maths required — the numbers are just symbols. You could replace 1–9 with any nine symbols and the puzzle would work the same way.

The golden rule: The same number can never appear twice in the same row, column, or box. If you see a conflict, something has gone wrong.

How to read the grid

A standard Sudoku grid is 9 cells wide and 9 cells tall — 81 cells total. It's divided into nine 3×3 boxes. When you start a puzzle, some cells already have numbers — these are called given numbers or clues. You need to fill in the rest.

On SudokuMaster.org, given numbers appear in dark text and your entries appear in purple. The board highlights your selected cell's row, column, and box automatically to help you see conflicts.

Your first solving strategy — step by step

Start with the most filled rows, columns, or boxes

Find a row, column, or box that already has 7 or 8 numbers filled in. With so few cells left empty, it's easy to figure out what's missing.

List what numbers are already there

Look at the row, column, or box. Which numbers 1–9 are already present? The empty cell must be one of the remaining numbers.

Cross-check with the row and column

For each empty cell, check which numbers are already in the same row AND the same column AND the same box. If only one number is possible, that's your answer.

Fill it in and keep going

After placing a number, re-scan the puzzle. Each correct placement may reveal new cells that can now be solved.

Use pencil marks when you get stuck

When no cell has only one possibility, write small candidate numbers in empty cells. On our site, click Notes to turn on pencil-mark mode. This lets you track possibilities and spot patterns.

Common beginner mistakes

Don't guess. Every valid Sudoku puzzle can be solved by logic alone. If you're guessing, you're likely missing a technique. Use Undo freely and try a different approach.

Forgetting to check all three units. Always check the row, column AND box together before placing a number.
Not using pencil marks. Even experienced players use notes. There's no shame — it's part of the technique.
Working too fast. Slow down and scan methodically. Rushing leads to errors that are hard to find later.
Fixing errors too late. Use the Check button regularly to catch mistakes early.

Start small — try 4×4 first

If 9×9 feels overwhelming, start with a 4×4 Easy puzzle. Same rules, just numbers 1–4, and four 2×2 boxes. Once that clicks, move up to 6×6, then the classic 9×9 Easy.

Features that help beginners

Highlights: When you select a cell, the row, column, and box all highlight — making it easy to spot conflicts.
Same-number highlight: All copies of the number in your selected cell glow softly across the board.
Notes mode: Toggle on to write candidates in small text. Toggle off to place the final number.
Hints: Stuck? Use a hint — it reveals one correct cell for you.
Undo: Made a mistake? Undo as many times as you need.
Auto-check: Errors flash red immediately so you know right away.

Ready to try your first puzzle?

Start with Easy difficulty — the perfect challenge for new players.

4×4 Easy — for beginners 9×9 Easy — classic