Naked triple

A naked triple is three cells in the same unit whose candidates collectively cover only three digits. Each cell can be a strict subset of the trio — one cell with {2, 5}, one with {2, 7}, one with {5, 7} — but together they use no more than three distinct digits. Those three digits must occupy those three cells, so they're eliminated everywhere else in the unit.

How to spot one

Three cells in a unit, each pencil-marked with two or three candidates, whose union is exactly three digits. The shapes vary: {2, 5} + {2, 7} + {5, 7} works, {2, 5, 7} + {2, 5, 7} + {2, 5, 7} works, {2, 5} + {5, 7} + {2, 5, 7} works. What matters is the union, not the per-cell symmetry.

Worked example: in box 6, three empty cells show pencil marks {1, 4}, {4, 8}, and {1, 8}. Their union is {1, 4, 8}. The three digits 1, 4, and 8 must occupy those three cells in some order. Every other cell in box 6 can have 1, 4, and 8 ruled out.

When you'll see it

Naked triples are noticeably trickier to spot than naked pairs because the three cells don't need matching pencil marks — they just need a shared three-digit pool. On medium puzzles they appear occasionally; on hard puzzles they're a regular workhorse, often the move that breaks open a stuck row or box. Like the naked pair, the triple itself rarely places a digit; it produces eliminations elsewhere that cascade into placements.

Why three is roughly the limit

Naked quadruples exist (four cells whose candidate union is four digits) but are rare in published puzzles — by the time you'd need them, simpler techniques have usually fired first. Triples sit at a sweet spot: enough complexity to be interesting, common enough to recognise, simple enough to verify by counting. Past the triple, the technique ladder shifts toward unit-spanning patterns like the X-wing.

For a longer take on naked vs hidden triples and how to scan for them, see Naked and hidden pairs and triples.