Classic 9×9
Standard Sudoku rules.
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Overview 
Sudoku
1 player · 5-25 min per session
Complete the selected grid size (9×9, 12×12, or 16×16) so that each row, column, and box contains no repeated numbers.
PuzzleNumber
Goal & Core Rules
Complete the selected grid size (9×9, 12×12, or 16×16) so that each row, column, and box contains no repeated numbers.
- Each row must contain every digit for that grid size exactly once.
- Each column must contain every digit for that grid size exactly once.
- Box rules change by difficulty: 3×3, 3×4, or 4×4 sub-boxes must also stay duplicate-free.
- Well-posed puzzles typically have a single unique solution.
Large 12×12
A bigger Sudoku variant using 3×4 boxes.
Large 16×16
An advanced large-grid Sudoku that uses 4×4 boxes and two-digit entry for 10–16.
Notes Mode
Track candidate digits as pencil marks. On mobile, use the Notes button; on desktop, use the menu or the N key.
Controls
Mouse
- Click a cell to select
- Use the on-screen number pad or keyboard to enter digits
- Use Clear or Backspace/Delete to erase
- Use the Notes button or menu to switch to candidate entry
Keyboard
- 1–9 to enter
- On 12×12 and 16×16 grids, enter 10+ as two consecutive digits
- Arrow keys move the current selection
- N toggles notes mode
- Backspace/Delete/0 clears the selected cell
Touch
- Tap to select
- Use the bottom or side number pad to enter digits
- Tap Notes to switch to candidate mode
- Tap Clear to erase the selected cell
Beginner Tips
- Start with singles: cells that have only one possible digit.
- Scan rows/columns/boxes for missing digits to spot easy placements.
- Use notes sparingly—write candidates where they meaningfully narrow choices.
Advanced Tips
- Hidden singles and pairs solve a large portion of puzzles without guessing.
- When stuck, revisit the most constrained unit (row/col/box) to eliminate candidates.
- Track which techniques you used by difficulty to improve faster.
Origins & History
The modern form appeared in 1979 in the U.S. as “Number Place,” was introduced in Japan by Nikoli in 1984 (which shortened the name to “Sudoku”), and then spread globally through newspapers in the mid-2000s.
Timeline
- 1979 Published by Dell as “Number Place.”
- 1984 Nikoli introduced it to Japanese readers; the long Japanese title was shortened to “Sudoku.”
- 2004 Widely syndicated in newspapers outside Japan, igniting a global boom.
Notable People
- Howard Garns Credited with creating “Number Place” (published in 1979)
- Nikoli Introduced it in Japan and popularized the name “Sudoku”
- Wayne Gould Helped popularize Sudoku in newspapers outside Japan in 2004
FAQ
Is Sudoku luck-based?
Proper Sudoku is designed to be solvable by logic, typically with a unique solution.
Do I need pencil marks?
Not required, but very helpful on intermediate and advanced puzzles.
Is guessing allowed?
You can, but focusing on logic techniques usually builds skill faster.