5 Basic Sudoku Strategies Every Beginner Should Know
Once you understand the rules of sudoku, the next step is learning how to solve puzzles efficiently. These five strategies cover everything you need for easy and medium puzzles.
Practice each one until it becomes second nature. When you can solve medium puzzles with these techniques alone, you're ready for advanced strategies.
1. Scanning (Cross-Hatching)
Scanning is the first technique every sudoku player learns. The idea is simple: pick a digit, then look at each 3×3 box to figure out where that digit can go.
How to do it: Say you're looking for 5s. Scan every row and column that already contains a 5. In each box, the cells crossed by these rows and columns cannot be 5. If only one cell in the box remains, that's the 5.
Scanning is fast, requires no notes, and often reveals several placements before you need anything else.
2. Naked Single
A naked single is a cell where only one digit can possibly go. You find it by checking the cell's row, column, and box, and eliminating every digit that already appears in any of them.
Example: If a cell's row contains 1, 2, 3, 5, 6, 7, 8, 9, and its column and box don't add any new information, then the only missing digit is 4. That cell must be 4.
Naked singles are the easiest placements to spot, especially when you have many filled cells around.
3. Hidden Single
A hidden single is the opposite of a naked single. Instead of looking at a cell and figuring out what digit it needs, you look at a digit and figure out where in a row, column, or box it must go.
How to find one: Pick a box. Look at a digit, say 7. Cross out every cell that is blocked by an existing 7 in the same row or column. If only one cell in the box remains, that's a hidden single — 7 must go there.
Hidden singles are extremely useful when a cell has many candidates but only one of them is valid in its box.
4. Block Elimination
This technique uses the box rule to narrow down candidates. In any box, if a digit can only go in cells that share the same row or column, then that digit can be eliminated from the rest of that row or column.
Example: In the top-left box, suppose 3 can only go in the two cells of the top row. That means the rest of the top row (outside the box) cannot contain 3. This is called "pointing" and is one of the most powerful intermediate techniques.
Block elimination and its cousin, box-line reduction, unlock most medium puzzles.
5. Naked Pair
A naked pair is when two cells in the same row, column, or box contain exactly the same two candidates — for example, both cells can only be 2 or 5.
Since those two digits must go in those two cells (in some order), you can eliminate 2 and 5 from every other cell in that row, column, or box.
Naked pairs often reveal hidden singles or open up block elimination opportunities. They are the gateway to more advanced techniques.
How to practice these strategies
The best way to internalize these techniques is to apply them one at a time:
- Week 1: Solve easy puzzles using only scanning and naked singles.
- Week 2: Add hidden singles. Notice how often they appear.
- Week 3: Learn block elimination. Try medium puzzles.
- Week 4: Practice naked pairs on harder puzzles.
Tip: Use our online sudoku with the timer on. It helps you track your progress and see which techniques you're already comfortable with.
What's next?
Once you can consistently solve medium puzzles using these five strategies, you're ready to move on. Learn advanced sudoku techniques like X-Wing, Swordfish, and XY-Wing to tackle hard and evil puzzles.
Or, if you want to practice with printed puzzles, browse our printable sudoku library — you can generate fresh puzzles at any difficulty.
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