Intermediate technique

Naked & hidden pairs in Sudoku: how to identify and eliminate digits

Learn the difference between naked and hidden pairs in Sudoku, how to use two candidates for safe eliminations, and the signs that make pairs easier to spot.

Practice at Hard level Read guide
Interactive technique example

See Naked Pair on a real grid

Read the candidate pattern first, then reveal the logical action. This example uses the same candidate rules as the site difficulty grader.

Technique detected: Naked Pair Find the highlighted pattern before revealing the move.
Why this move?

The same two candidates occupy exactly two cells in row 2, so those digits are reserved for the pair.

Action: Keep 2 and 3 in the pair and remove those candidates from the other highlighted cells.

9
1
2
6
23
8
9
1
23
23
23
5
5
7
8
1
1
4
2
2
9
4
8
7
2
9
1
2
5
1
3
4
6
7
9
8
3
8
9
7
1
5
2
8
9
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3
Pattern Candidate to remove Logical result
Naked pair

Two cells contain exactly the same two candidates

In a row, column, or block, if exactly two cells each contain the same two candidates, for example {2,8}, then 2 and 8 must occupy those two cells in some order. Therefore 2 and 8 can be removed from every other cell in that region.

You do not need to know which cell is 2 and which is 8. The value of a naked pair is that the two digits reserve those two cells, freeing those candidates from the other cells in the region.

  • The two cells must be in the same region.
  • Each cell must have exactly two candidates remaining, and the two candidate sets must match.
  • Only eliminate those two candidates from other cells in the same region.
Hidden pair

Two digits have exactly two positions left

A hidden pair is the reverse view. In a region, if digits 3 and 6 can only appear in the same two cells, those two cells must be reserved for 3 and 6 even if they currently contain extra candidates. You can remove the extra candidates and turn the hidden pair into a clear pair.

Hidden pairs are harder to spot because the two cells may currently contain four or five candidates. Instead of looking at each cell, track each digit's positions across the whole region and find two digits that share exactly two positions.

Distinguish

Look at cells for naked pairs; look at digits for hidden pairs

A simple way to remember it: a naked pair starts with two cells that share the same candidates; a hidden pair starts with two candidates that appear only in the same two cells. Both use the principle that two digits must occupy two positions, but the starting observation is different.

After finding a pair, do not stop after removing candidates. Check the cells you just narrowed; they may become singles, form another pair, or lock a candidate into a row or column.

Avoid mistakes

Do not call every two similar cells a pair

If two cells contain {2,8,9}, they are not a naked pair because a third candidate remains. If candidates 3 and 6 both appear in two cells but 3 also appears in a third cell in the region, they do not form a hidden pair either. Verify the full conditions before eliminating anything.

Pairs commonly appear in Medium–Hard Sudoku and form the foundation for triples and quads. Master pairs before learning larger subsets and you will read candidates much faster.

Apply it immediately on a real puzzle

A technique becomes automatic only after you use it across many different boards. Play at a manageable level, prioritize certain deductions, and review the step that caused you to get stuck.

Practice at Hard level
Learn by technique

Sudoku solving guide cluster

How to Solve Sudoku

Each guide below targets a distinct search intent and skill, from a beginner workflow to locked candidates, pairs, and X-Wing. Follow them in order if you are unsure where to start.

How to solve Sudoku: techniques from basic to advanced A systematic Sudoku solving path: scan singles, manage candidates, use pairs, locked candidates, and advanced patterns without guessing. Sudoku Tips for Beginners: Solve Faster with Fewer Mistakes Practical Sudoku tips for beginners: scan regions, choose good starting points, use Notes at the right time, and avoid habits that make easy games confusing. Naked Single Sudoku – Find Forced Cells Fast Learn how to spot a Naked Single in Sudoku, verify the only candidate left in a cell, and turn forced cells into a reliable solving loop. Hidden Single Sudoku – Find the Only Place Learn Hidden Singles in Sudoku: track one digit across a row, column, or box, find its only legal position, and avoid confusing them with Naked Singles. Sudoku Candidates & Pencil Marks – Practical Guide Use Sudoku candidates and pencil marks accurately: calculate legal digits, keep notes updated, and prepare for Locked Candidates, Pairs, and X-Wing. Locked Candidates in Sudoku: Pointing & Claiming Explained Understand locked candidates in Sudoku through pointing and claiming, how to identify the pattern, eliminate candidates in the right places, and avoid common mistakes. What Is X-Wing in Sudoku? How to Spot and Use It Correctly A step-by-step X-Wing Sudoku guide: four-corner conditions, row/column scanning, candidate elimination, and patterns that are easy to misread.