Minimal Sudoku
Minimal Sudoku Online
Learn Section

The Ultimate Beginner's Guide to Sudoku

Learn scanning, naked singles, and pencil marks to solve your first puzzles

By Minimal Sudoku TeamLast updated:

Want to learn how to play Sudoku? This addictive number puzzle is easier to master than you think! This guide will take you step-by-step through the rules, essential techniques, and get you solving your first puzzles in minutes.

⚡Quick Summary
  • Rules: Fill the grid so each row, column, and box has 1-9
  • Scanning: Find cells where only one number can go
  • Naked Singles: One candidate left in a cell
  • Pencil Marks: Track possible candidates

Sudoku Rules — Just Two Simple Rules!

The beauty of Sudoku is in its elegant simplicity. You only need to grasp these core principles:

📜 The Three Constraints
  1. Every row must contain numbers 1-9 with no repeats
  2. Every column must contain numbers 1-9 with no repeats
  3. Every 3×3 box must contain numbers 1-9 with no repeats
Rule 1: Numbers 1-9 in Every Row
Rule 2: Numbers 1-9 in Every Column
Rule 3: Numbers 1-9 in Every Box
Logic Over Luck
Well-designed Sudoku puzzles are solvable using logic alone — no guessing required! If you feel tempted to guess, pause and look again. There's likely a logical step you've overlooked.

Scanning: Your First Technique

Scanning is a systematic way to analyze the grid and find cells where only one number fits. It's all about elimination based on the Sudoku rules.

1

Focus on a number

Start with 1 and systematically go through all numbers to 9.
2

Scan rows and columns

Look at where this number already exists in the grid.
3

Eliminate possibilities

Cross out rows, columns, and boxes where the number can't go.
4

Find the hidden single

If only one cell remains in a box, that's where the number goes!
Scanning example: 1 must go in row 4, column 3

For more details, see our Scanning Technique guide.

Naked Singles: Spotting the Obvious

A Naked Single occurs when only one number can legally go in a cell — all other numbers are already present in its row, column, or box.

1

Pick an empty cell

Choose any empty cell on the grid.
2

Check row, column, and box

Note all numbers already present in the cell's row, column, and box.
3

Eliminate candidates

Cross off numbers that can't go in this cell.
4

Find the single

If only one number remains, that's your Naked Single!
Naked Single Example

Pencil Marks: Track Your Candidates

Pencil marks (also called candidates or notes) are small numbers you write in cells to track possible values. They're essential for harder puzzles.

✏️ Why Use Pencil Marks?
  • Track possibilities visually
  • Reveal hidden patterns
  • Reduce guessing, promote logic
  • Essential for medium+ difficulty
Example of Pencil Marks

Learn more in our Pencil Marks guideor try Snyder Notation for a more efficient approach.

Tips for Beginners

Start with Easy Puzzles
Don't jump into expert puzzles! Begin with Easy difficulty to build confidence.
Use Pencil Marks Early
Don't wait until you're stuck. Start using pencil marks as soon as puzzles get tricky.
Be Systematic
Develop a routine: scan for each number, look for naked singles, then use pencil marks.
Practice Regularly
Even 15-20 minutes daily will dramatically improve your skills.

Try It Yourself!

Ready for More?

Master these basics, then level up with advanced techniques.

Learn Snyder Notation

Continue Learning

Next Steps

✏️Snyder Notation👥Naked Pairs🔎Hidden Singles📚All Strategies
Snyder Notation: Your Next StepIntermediate

Snyder Notation: Your Next Step

A powerful notation technique that makes solving faster and more intuitive.