Learn How to Play Sudoku

A clear step-by-step guide to rules, essential techniques, and logic featuring two interactive practice exercises.

Fundamental Rules

The 3 Golden Rules of Sudoku

Sudoku is played on a 9×9 grid divided into nine 3×3 boxes. The game involves no arithmetic or calculation – only keen observation and deductive logic!

↔️

Every Row

Each horizontal row must contain the numbers 1 through 9 exactly once.

↕️

Every Column

Each vertical column must contain the numbers 1 through 9 exactly once.

🔲

Every 3×3 Box

Each of the nine 3×3 sub-grids must contain the numbers 1 through 9 exactly once.

Golden Rule: No number may ever repeat within the same row, column, or 3×3 box!

Exercise 1 of 2: Cross-Hatching (Scanning)

Where Must the 8 Go?

Cross-hatching is the most essential scanning technique in Sudoku. Look at the three boxes below:

  • Box 1 already has an 8 in row 1. Therefore, no other cell in row 1 can be an 8.
  • Box 2 already has an 8 in row 2. Therefore, no other cell in row 2 can be an 8.
  • Objective: In Box 3 (on the right), rows 1 and 2 are blocked. Which cell must contain the 8?

Tap the yellow highlighted cell where 8 must go, then select 8 on the numpad below:

8
1
3
4
9
2
🚫
7
5
7
4
2
8
5
6
🚫
3
1
9
5
6
1
3
7
?
4
2
Exercise 2 of 2: The Final Push on a 9×9 Board

Solve the Final 4 Cells

Here is an authentic Sudoku puzzle where 77 of 81 cells are already solved! Only 4 cells remain.

Tap one of the yellow cells. Notice how the row, column, and 3×3 box light up to reveal missing numbers. Select the correct digit from the numpad:

5
3
4
6
7
8
9
?
2
6
7
2
1
9
5
3
4
8
1
9
8
3
4
2
5
6
7
8
5
9
7
6
1
4
2
3
4
2
6
8
?
3
7
9
1
7
1
3
9
2
4
8
5
6
?
6
1
5
3
7
2
8
4
2
8
7
4
1
9
6
3
5
3
4
5
2
8
6
1
7
?
Pro Tips

3 Golden Tips to Solve Faster

  • Start with the most frequent digits: If six 7s are already placed, you can almost always find the remaining three quickly using cross-hatching.
  • Use pencil notes ✏️: Tap the pencil icon to jot down candidate digits in empty cells when weighing options.
  • Never guess: A single guessed mistake cascades across the board. If you are stuck, look for easier rows, columns, or boxes!

Ready to Master Sudoku!

You have practiced core logic hands-on. Start with an Easy puzzle and feel the satisfaction of cracking it!

Start Level 1 (Easy) 🟢 Browse All Boards 📋
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