What is Sudoku?
Sudoku is a logic-based number placement puzzle. Fill a 9×9 grid with digits 1-9 so that each row, column, and 3×3 box contains all digits without repetition.
Every puzzle has exactly one solution reachable through pure logic—no guessing required. PencilGrid's engine guarantees unique solutions and logic-only solving paths. Difficulty ratings reflect how many cells are given and how deeply you must apply elimination logic.
The daily follows a weekday curve: Monday-Tuesday are Easy, Wednesday-Thursday are Medium, Friday-Saturday are Hard. Sunday resets to Easy. Practice mode offers unlimited puzzles at your chosen difficulty.
Features
Daily Puzzles
New puzzle every day at midnight UTC. Build a streak by solving consecutive days.
Practice Mode
Unlimited puzzles at Easy, Medium, and Hard difficulty. Perfect for learning or warming up.
Notes Mode
Pencil in candidate numbers (notes) in each cell. Essential for advanced solving techniques.
Hints
Get tactical hints that teach solving techniques. Hints highlight cells and explain the logic.
Error Checking
Check your work at any time. Conflicts are highlighted so you can find and fix mistakes.
Undo/Redo
Full undo/redo stack. Experiment freely without fear of losing progress.
How to Play
The Rules
1.
Each row must contain the digits 1-9 without repetition.
2.
Each column must contain the digits 1-9 without repetition.
3.
Each 3×3 box must contain the digits 1-9 without repetition.
Basic Strategy
Start by scanning for cells where only one number is possible. Look for rows, columns, or boxes that already have many numbers filled in. Use notes mode to track candidates in difficult cells. The puzzle always has exactly one solution reachable through logic alone.
Frequently Asked Questions
Is PencilGrid Sudoku completely free?
Yes, all Sudoku puzzles on PencilGrid are completely free. No account, subscription, or payment required. Play as much as you want.
When does the new daily puzzle become available?
A new daily Sudoku puzzle is published every day at midnight UTC. You can complete previous dailies even if you missed them.
Do I need to create an account?
No account needed. Your progress is saved locally in your browser using IndexedDB. This means your game state persists across sessions on the same device and browser.
Can I play on mobile?
Yes! PencilGrid Sudoku works on all devices. The interface adapts to touch input on mobile and tablets, with full keyboard support on desktop.
What difficulty levels are available?
Daily puzzles have varying difficulty. Practice mode offers Easy, Medium, and Hard levels. Each difficulty is carefully calibrated to provide an appropriate challenge.
Explore More
Daily Sudoku
Learn about the daily puzzle, difficulty rotation, and how to play.
Play Today's Puzzle
Solve today's daily Sudoku and maintain your streak.
Practice Mode
Unlimited puzzles at Easy, Medium, and Hard difficulty levels.
Play Nonogram
Try our picture logic puzzle game - reveal hidden images using row and column clues.