What are the rules of Sudoku?

Fill a 9×9 grid so every row, column, and 3×3 box contains the digits 1–9 exactly once. No math is required — it is pure logic and elimination.

Step-by-step: How to start a Sudoku puzzle

1. Choose a difficulty level from the toolbar
2. Survey the pre-filled cells — note which digits appear most
3. Find rows, columns, or boxes that have the most clues
4. Eliminate candidates for each empty cell
5. Enter the digit you're certain about

Solving strategy: Elimination

Start with the digit that appears most often in the grid. For each 3×3 box where it's missing, narrow down which cells it can still occupy. Cross-reference the row and column to eliminate options until only one cell remains.

Solving strategy: Naked Singles

A naked single is a cell with only one valid candidate after eliminating all digits already in its row, column, and box. These are the most common clues in Easy and Medium puzzles.

Solving strategy: Hidden Singles

A hidden single is a digit that can only go in one cell within a row, column, or box — even if that cell appears to have multiple candidates. Scan each unit for digits that have only one possible placement.

Advanced: Naked Pairs

When two cells in the same row, column, or box share exactly the same two candidates, those two digits can be eliminated from every other cell in that unit. This is the first advanced technique needed for Hard and Expert puzzles.

Difficulty levels explained

Controls reference

Top 5 tips for beginners

1. Start with Easy difficulty until you can complete a puzzle without mistakes.
2. Always scan the entire grid before entering a digit — a digit you're sure about in one box often resolves neighbouring boxes.
3. Use pencil marks (notes) to track candidates in cells before committing to a value.
4. Prioritise rows, columns, and boxes that already have seven or more digits filled.
5. When stuck, switch to the Hint feature rather than guessing — every guess that's wrong costs a mistake.