Hidden Single

The Basics4 / 32

The digit fits nowhere else in the row or column.

A cell can have plenty of candidates and still be forced: if a digit has no other home in the cell's row or column, that cell must take it — the other candidates are a distraction.

That's why it's called hidden: the single is buried under other pencil marks and only shows itself when you track one digit across the whole unit.

See it in action

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Step 1 of 4

The setup

Track one digit at a time along a row or column: mark every cell where it's still allowed. If you end up with a single spot, you've found it. Step through this real position to see it happen.

Practice

In one row or column, a digit has exactly one legal cell left. Place it there.

Drill 1 of 29

Tap the cell, then the digit — or type it.