Easy technique · Technique Academy

Hidden Single

A hidden single is a digit that has only one cell left to live in within a row, column or box. That cell may list other candidates too, but it is the only home this digit has there.

Professor Cryptic, the owl who teaches in the app
Professor Cryptic is thinking

The reasoning

Why does the Hidden Single work?

Pick a digit and a unit, and ask where it can still go. If the answer is one cell, it goes there, however crowded that cell's notes look.

A worked example

What does the Hidden Single look like on a real board?

Hidden Single worked exampleA sudoku board with pencil marks. The Hidden Single uses R3C8 and digit 2 (row 3). The move places 2 in R3C8.42135781386935858357857895673567892347847815683567878671367851378178429593569712458912482568912456891456815643689235892872568956857982146914591456931456395814814865872645757814891247893589145891458278178489247895368946893468
The move places 2 in R3C8. Digit 2, row 3.
  • The cell that decides

Make it stick

How can you practise the Hidden Single?

The Technique Academy in Cryptic gives every technique its own lesson and 5 practice boards that need exactly this move.

Get it onGoogle PlayPlay Cryptic on the web

Further reading: HoDoKu's page on this family of techniques.

EasierNaked SingleHarderNaked Pair