Hidden Single
Prerequisites: Naked Single
Overview
When a candidate appears in only one cell within a house, it must go there -- even if the cell has other candidates.
How It Works
For a given digit and house, if only one cell can hold that digit, it must be placed there. The answer is 'hidden' among the cell's other candidates.
When To Use It
After setting pencil marks, scan each house for digits that appear in only one cell's candidate list.
How To Detect It
For each digit 1-9, check each row, column, and box. If a digit's candidates reduce to a single cell, place it.
Visual Example
Step 1 of 8
Hidden Behind Other Candidates
A Hidden Single occurs when a digit can go in exactly one cell within a house (row, column, or box) — even if that cell has other candidates too. The digit is 'hidden' among them.
Practice
Hit 'Show Candidates', then find a digit that can go in only one cell of a house and place it.