Sudoku Tips & Strategies: Solve Puzzles Faster

You know the basic rules of Sudoku and can solve Easy puzzles. Now it’s time to level up. This guide covers the intermediate techniques that will help you conquer Medium and Hard puzzles with confidence.

Quick Recap: The Two Basic Techniques

Before diving into new strategies, make sure you’re comfortable with these two fundamentals:

  • Naked Single — a cell where only one candidate remains after elimination.
  • Hidden Single — a digit that can only go in one cell within a row, column, or box.

These two techniques can solve most Easy and many Medium puzzles. But when they’re not enough, you need the strategies below.

Technique 1: Naked Pairs

Intermediate

A Naked Pair occurs when two cells in the same group (row, column, or box) have exactly the same two candidates and nothing else. Since these two cells must contain those two digits, you can eliminate both digits from all other cells in that group.

1 How to spot a Naked Pair

Look for two cells that share the same two candidate numbers. Example: two cells in a row both have candidates {3, 7}. Since one must be 3 and the other must be 7, no other cell in that row can be 3 or 7.

Example: Naked Pair in a row
1
2 3 4
2 3 4
3
3
4
1
2
2
1
4
3
4
3
2
1

Row 1, cells 2 and 3 both have candidates {2, 4}. This is a Naked Pair — so 3 and 4 can be eliminated from other cells in that row (if any existed). The crossed-out 3 and 4 show eliminated candidates.

Technique 2: Hidden Pairs

Intermediate

A Hidden Pair is the inverse of a Naked Pair. It occurs when two digits can only appear in two cells within a group — even though those cells may have additional candidates. Since those two digits are locked into those two cells, you can remove all other candidates from those cells.

2 How to spot a Hidden Pair

Instead of looking at cells, look at digits. For each digit, count how many cells in a group can hold it. If two digits share exactly the same two possible cells, you’ve found a Hidden Pair.

Technique 3: Pointing Pairs

Intermediate

A Pointing Pair occurs when a candidate digit within a 3×3 box is restricted to a single row or column. Since that digit must appear in that row/column within the box, you can eliminate it from the same row or column outside the box.

3 How Pointing Pairs work

Example: In a 3×3 box, digit 5 can only appear in the top row (cells in row 1). This means 5 must be in row 1 within that box. Therefore, 5 cannot appear anywhere else in row 1 outside this box. Eliminate 5 from row 1 in the other two boxes.

Example: Pointing Pair in the top-left box
5
2
5
7
8
4
7
1
9
2
6
5
8
4
6
3
9
3
7
1
7
9
1
9
4
7
8
4
3
2
1

In the purple top-left box, digit 5 can only appear in yellow cells (row 1). So candidate 5 is eliminated from the blue cells in row 1 outside the box.

Technique 4: Box/Line Reduction

Intermediate

Box/Line Reduction is the reverse of Pointing Pairs. When a candidate digit in a row or column is confined to a single 3×3 box, you can eliminate that digit from other cells in the box.

4 How Box/Line Reduction works

Example: In row 5, digit 7 can only appear in cells that are all within the same 3×3 box. Since 7 must appear somewhere in row 5, and all its possible locations are in that box, 7 cannot appear in any other cell of that box outside row 5.

Technique 5: Naked Triples

Intermediate

A Naked Triple extends the Naked Pair concept to three cells. When three cells in the same group contain only three distinct candidates between them (e.g., {2, 5}, {2, 8}, {5, 8}), those three digits are locked into those three cells. Eliminate them from all other cells in the group.

Note: the three cells don’t each need all three candidates. The key is that combined, they contain exactly three distinct digits.

General Solving Tips

  1. Always fill in pencil marks first — most intermediate techniques require candidates to be visible.
  2. Scan systematically — go through each row, then each column, then each box looking for patterns.
  3. Focus on constrained areas — rows, columns, or boxes with the most given digits have fewer empty cells and are more likely to yield results.
  4. Look for the technique, don’t force it — if you can’t find a Naked Pair, try Hidden Pairs. If that fails, try Pointing Pairs. Cycle through techniques.
  5. Update pencil marks after every placement — a single new digit can trigger a chain of eliminations.
  6. Use Sudoku School’s hint system — our Explain button automatically fills in pencil marks and shows you the next logical step.

When to Move to Advanced Techniques

If you’ve mastered all the techniques above and still encounter puzzles you can’t crack, it’s time to learn advanced techniques like X-Wing, Swordfish, and Unique Rectangle. These patterns involve looking across multiple rows and columns simultaneously.

Check out our Advanced Sudoku Techniques guide to continue your journey.

What’s Next?

Put these strategies into practice: