Sudoku Hidden Pair
See a hidden pair on a real puzzle, or paste your own and find it.
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A hidden pair is two digits that can go in only the same two cells of one row, column or box. This page has a free tool that finds the first place this technique is the next move in a sudoku puzzle and shows which candidates can be removed.
The tool runs in your browser. It needs no sign-up and nothing to install, and nothing is uploaded. It shows a 9×9 sudoku with pencil marks, so every empty cell lists the digits that can still go there. You can start with one of four example puzzles or paste your own. The page does not play the puzzle for you. It finds and explains one technique at a time, so you can learn the pattern before trying it on a grid of your own.
How to use the sudoku hidden pair tool
- Open the page. It starts on Example 1, a real puzzle where a hidden pair is the next move.
- To try another puzzle, open the menu “Example puzzles” and choose Example 1 to Example 4. Choosing one starts the search again.
- To use your own puzzle, paste or type 81 characters into “Your own puzzle”, one per cell. Use the digits 1 to 9 for given digits and a dot or 0 for an empty cell. Spaces and line breaks are ignored.
- Press the button “Find Hidden Pair in my puzzle”.
- Read the message under the board. It gives the number of simpler steps used first, names the exact cells and digits, and says what to remove.
- Look at the board. Yellow cells are the pattern, blue cells are the row, column or box involved, and red circles mark the candidates that can be removed.
- Press “Apply it and find the next one” to remove the red candidates, solve on with the easier techniques, and show the next place the hidden pair works. Press “Start over” to go back to the first one.
If your text is rejected, a red message says why. Common reasons are a wrong length, a character that is not a digit or an empty cell, two equal digits in one row, column or box, or no solution. A note appears if the puzzle has more than one solution; the moves shown are still valid logic.
What is a hidden pair in sudoku?
A hidden pair is two digits that can go in only two cells of the same row, column or box. Those two cells must hold exactly those two digits, so every other candidate in them can be removed. The hidden pair technique is one of the 12 techniques the site’s solver uses, and it belongs to the Medium level.
How do you find a hidden pair?
Pick a row, column or box with pencil marks, then list the cells where each digit can go. If two different digits have the same two cells, you have found a hidden pair.
- Choose one row, column or box.
- For each digit, note the cells that still hold it as a candidate.
- Look for two digits whose lists are exactly the same two cells.
- Remove all other candidates from those two cells.
In Example 1, row 1 has the digits 4 and 9 only in R1C6 (candidates 4, 8, 9) and R1C8 (candidates 4, 7, 9). Those cells must be 4 and 9, so 8 is removed from R1C6 and 7 from R1C8.
What is the difference between a hidden pair and a naked pair?
A naked pair is two cells that hold only the same two candidates, and those digits are removed from the other cells of the unit. A hidden pair is two digits that fit only in the same two cells, and the removals happen inside those two cells. A naked pair cleans up the other cells; a hidden pair cleans up the pair cells themselves.
Can a hidden pair be in a row, a column or a box?
Yes. The rule is the same in any of the three. In Example 2, row 3 has the digits 2 and 6 only in R3C1 (candidates 1, 2, 6) and R3C9 (candidates 2, 4, 6). So 1 is removed from R3C1 and 4 from R3C9.
How often does a hidden pair appear?
In tests on the site’s own generator, a hidden pair was the next move at some point in 11.7 % of 1,500 random single-solution puzzles with 22 to 27 clues. That is about 1 puzzle in 9. The puzzles were not graded by difficulty.
Frequently asked questions
Does the tool place digits for me?
No. The pattern techniques only remove candidates. A digit is placed once a cell has only one candidate left.
Is each removal certain?
Yes. Each removal follows from the rules of sudoku, so nothing is guessed. The tool checks its examples against a brute-force solver, and no removed candidate is the solution digit.
What if my puzzle never shows a hidden pair?
The message will say so. The puzzle may be solved with other techniques, or it may need a harder technique or a guess.
Can I paste a newspaper puzzle?
Yes. Copy the 81 cells as text, using digits for given numbers and a dot or 0 for empty cells. Line breaks and spaces are ignored.
How common is a hidden pair?
In 1,500 random single-solution puzzles made by this site, a hidden pair was the next move at some point in about 12 % of them, roughly 1 puzzle in 9. It belongs to the Medium level here.
What is the difference between a hidden pair and a naked pair?
A naked pair is two cells that hold only the same two candidates, which are then removed from the rest of the unit. A hidden pair is two digits that fit only two cells, and the other candidates are removed from those two cells.
Related tools
- How to play sudoku: Read this first if you are new to the rules and the basic moves.
- Medium sudoku: Use this when you want puzzles at the level where hidden pairs first appear.
- Sudoku solver: Use this to solve a full puzzle when you want the answer.
- Hard sudoku: Use this when you want harder puzzles that need rarer techniques.
- Sudoku generator: Use this to create new puzzles to practise on.
- Easy sudoku: Use this for simpler puzzles that do not need pair techniques.
- Daily sudoku: Use this for a new puzzle each day.
- Printable sudoku: Use this when you want to solve on paper with pencil.