Hidden Singles and Hidden Pairs: The Sudoku Techniques Beginners Miss
Quick answer: A hidden single is a number that can only go in one cell of a row, column, or box — even if that cell shows other candidates. A hidden pair is two numbers that can only go in the same two cells of a house. Both let you make progress when the grid looks stuck.
Most beginners learn to hunt for naked singles — cells with only one candidate left. But the most common reason players get stuck is that they miss the hidden versions. Here is how to find them.
How to find a hidden single
A hidden single hides in plain sight. The trick is to focus on a number, not a cell.
- Pick a house (a row, column, or 3x3 box).
- For one digit, check how many empty cells in that house could still accept it.
- If the answer is exactly one cell, place it — even if that cell also lists other candidates.
The digit is “hidden” because the cell looks busy with pencil marks, but logically that number has nowhere else to live.
How to find a hidden pair
A hidden pair is the two-number version of the same idea.
- Look for two digits that can only appear in the same two cells of a house.
- Those two cells might also show three or four other candidates — ignore them.
- Since the pair must occupy those two cells, you can safely erase every other candidate from both cells.
This often turns a cluttered pair of cells into a clean naked pair, which then unlocks further eliminations.
Why these matter
Hidden singles and pairs are the bridge between basic crosshatching and intermediate techniques like naked pairs and pointing groups. Master them and most medium puzzles open right up.
Want to practice? Turn on automatic pencil marks in the Sudoku Aura app to see hidden patterns without manual notation, or play a free puzzle here.