How to Play Sudoku: A Complete Beginner’s Guide
Sudoku is one of the world’s most popular logic puzzles. It requires no math — just pure reasoning and pattern recognition. Whether you’re a complete beginner or looking to sharpen your skills, this guide will walk you through everything you need to know.
What Is Sudoku?
Sudoku is a number-placement puzzle played on a 9×9 grid. The grid is divided into nine 3×3 boxes (also called “regions” or “blocks”). Some cells are pre-filled with digits — these are called givens or clues.
The One Rule of Sudoku
Fill every row, every column, and every 3×3 box with the digits 1 through 9, using each digit exactly once per group. That’s it — one rule to master!
Here’s a small 4×4 example to visualize the concept. Every row, column, and 2×2 box must contain 1–4 exactly once:
Given digits have a bold dark background. Solved digits are shown in blue.
Step 1: Scan Rows, Columns, and Boxes
Start by scanning each row, column, and 3×3 box to see which digits are already placed. This helps you figure out what’s missing.
In the example below, focus on the highlighted row. It already contains 5, 3, 7, and 6. That means this row still needs 1, 2, 4, 8, and 9.
The highlighted first row already has 5, 3, 7 — so we know it still needs 1, 2, 4, 6, 8, 9.
Step 2: Use Elimination
Elimination (also called “cross-hatching”) is the core Sudoku habit. Instead of guessing what fits in a square, you ask a tighter question: which digits are already blocked by the row, the column, and the box? Whatever survives that test is the real candidate list.
In practice, strong beginners do not solve one cell in isolation. They move back and forth between groups, letting the row remove one option, the column remove another, and the box finish the job.
Step 3: Use Pencil Marks (Candidates)
Pencil marks (also called candidates or notes) are small numbers written into empty cells to track what is still legally possible. They turn a vague puzzle into visible logic, which is why they matter so much on medium and harder boards.
In the example below, each empty cell shows its candidate digits in a 3×3 mini-grid layout (positions correspond to digits 1–9). Hover for layout details.
Crossed-out numbers have been eliminated. Green bold numbers are confirmed candidates. When only one candidate remains, that’s your answer!
Step 4: Find Naked Singles
A Naked Single occurs when a cell has only one possible candidate left after elimination. This is the easiest technique — if a cell can only be one digit, fill it in!
In the board above, look at cells where only one green number appears. Those are Naked Singles — you can fill them in immediately.
Step 5: Find Hidden Singles
A Hidden Single occurs when a digit can only go in one cell within a particular row, column, or box — even if that cell has multiple candidates. Since no other cell in that group can hold that digit, it must go there.
This is slightly harder to spot than Naked Singles, but it’s one of the most powerful basic techniques.
Advanced Techniques
Once you’re comfortable with the basics, you can explore more advanced strategies:
- Naked Pairs / Triples: When two (or three) cells in the same group share the same two (or three) candidates, those digits can be removed from other cells in that group.
- Pointing Pairs: When a candidate in a box is restricted to a single row or column, it can be eliminated from that row/column outside the box.
- Box/Line Reduction: The reverse of Pointing Pairs — when a candidate in a row/column is confined to one box.
- X-Wing: A pattern across two rows and two columns that allows eliminations.
Don’t worry about these right away! Master the basics first, and these techniques will come naturally as you tackle harder puzzles.
Tips for Success
- Start with easy puzzles until scanning and singles feel automatic.
- Use pencil marks early instead of waiting until you feel stuck.
- Work systematically — scan rows, then columns, then boxes, rather than bouncing randomly around the grid.
- Do not guess out of frustration — if a move is unclear, there is usually a missed candidate or overlooked group interaction.
- Take short breaks when the board feels noisy — a reset often reveals the next clean deduction.
Ready to Play?
Now that you know the rules and the first layer of solving logic, the best next step is repetition. Start with Easy Sudoku if you want to build confidence, move to Medium Sudoku when notes start to feel natural, and save Evil or Extreme Sudoku for when you want to test real pattern recognition.
If you want a fresh puzzle every day, try Daily Sudoku. If you are checking a difficult grid or verifying your own solve, use the Sudoku Solver. If you prefer pencil-and-paper play, you can also print Sudoku puzzles.
For a deeper learning path, continue with our complete beginner’s guide, then read tips and strategies, and finally move on to advanced techniques such as X-Wing and Swordfish.