Hidden Triples in Sudoku: Find the Digits Hiding in Plain Sight

Naked triples are visible in the cells; hidden triples are visible in the digits. Three digits may appear only in the same three cells while those cells carry distracting extra marks.

Once found, the extra candidates can be removed and the reserved structure becomes clear.

Choose a unit and three digits

Scan a row, column or box for three digits whose possible positions are contained in the same three cells. The digits may appear in two or three of those cells, but nowhere else in the unit.

Ignore the extra marks temporarily

The three cells may contain four or five candidates each. Those extras are the disguise. What matters first is that the chosen digits cannot escape the three-cell set.

Trim the cells

Remove every candidate from those cells except the hidden triple’s three digits. This is the reverse of a naked triple: you are cleaning the cells after proving the digit positions.

Check for a simpler result

The trimmed cells may become a pair, a single or a clean triple. Use the new information immediately instead of leaving the pattern as an isolated note.

Avoid overclaiming

Three digits appearing in three cells is not enough if one of those digits has a position outside the set. Recheck every occurrence before eliminating anything.