Rows
Rows go across the board.
5
3
7
6
1
9
5
9
8
6
8
6
3
4
8
3
1
7
2
6
6
2
8
4
1
9
5
8
7
The Goal
Fill every row, column, and bold 3×3 box with the numbers 1 to 9. A number cannot repeat in the same row, column, or box.
Board Basics
Some squares already have numbers when the puzzle starts. Those are givens: they stay fixed, and you fill the empty squares.
- A row runs left to right.
- A column runs top to bottom.
- A bold 3×3 box is one of the nine smaller sections of the board.
- Given numbers appear fixed; numbers you add can be changed.
Columns
Columns go up and down.
5
3
7
6
1
9
5
9
8
6
8
6
3
4
8
3
1
7
2
6
6
2
8
4
1
9
5
8
7
3×3 Boxes
Bold lines split the board into nine boxes.
5
3
7
6
1
9
5
9
8
6
8
6
3
4
8
3
1
7
2
6
6
2
8
4
1
9
5
8
7
Making Moves
- Select an empty square, then choose the number you want to place.
- Use erase or undo when you want to change a number you added.
- You cannot change the given numbers that were on the puzzle at the start.
- Before placing a number, check that it does not already appear in the same row, column, or 3×3 box.
Check before you place
For one empty square, check its row, column, and 3×3 box.
5
3
6
7
8
9
1
2
6
1
9
5
9
8
6
8
6
3
4
8
3
1
7
2
6
6
2
8
4
1
9
5
8
7
Pencil Mode
Pencil Mode lets you add small notes inside a square. Use notes when you are not ready to choose one final number yet.
- Pencil marks are reminders, not answers.
- You can add or remove notes as the board changes.
- Harder puzzles often need notes before the next correct number becomes clear.
Notes inside a square
Small numbers show what might fit later.
5
3
7
6
1
9
5
9
8
6
8
6
3
4
8
2
5
7
9
3
1
7
2
6
6
2
8
4
1
9
5
8
7
Helpful Tools
- Hints: get a nudge when you are stuck.
- Auto-check: show incorrect entries while you play.
- Row and column guide: highlight the selected square’s row and column.
- Timer: track your solve time, or turn it off for a calmer puzzle.
Difficulty Levels
- Easy: smooth starts and frequent singles.
- Medium: stronger cross-checking and note cleanup.
- Hard: more advanced elimination patterns.
- Expert: deeper chains and tougher endgames.
- Legendary: maximum pressure, minimal freebies.
Sudoku Race
Sudoku Race uses the same board rules, but two players solve the same puzzle live.
- Create a private invite on Sudoku Race and send it to a friend.
- The guest opens the link and taps Join lobby to claim the seat.
- Both players mark ready, and the host starts the race.
- The first correct finish wins. Before the start, the guest can leave and the host can kick the guest to reopen the seat.
Quick Tips
- Start with rows, columns, or boxes that are almost filled in.
- Use logic and process of elimination first; save guessing for true dead-ends.
- Use Pencil Mode when you have several possible numbers in a square.
- When a puzzle gets harder, learn the named patterns in the Techniques guide.
Ready to play? Try a puzzle or browse most popular boards.
Want a visual solving flow? Open the Walkthrough.
Need exact rule details? Read the Sudoku Rules.