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Sudoku Tips & Strategies

Every Sudoku is solvable by logic alone. These techniques — roughly easiest to hardest — are the tools that get you there, whether you're stuck on Easy or chasing an Expert clean run.

Good habits first

• Scan, don't stare. Sweep whole rows, columns and boxes rather than fixating on one empty cell.
• Work one digit at a time. Ask "where can a 7 go in this box?" — it surfaces placements you'd otherwise miss.
• Pencil in candidates. Notes turn a fuzzy grid into a clear one. On Playoku, toggle notes mode and mark every possibility.
• Never guess. Guessing leads to dead ends. If nothing's obvious, a harder technique applies — find it.

Beginner techniques

Naked single

After eliminating every digit already present in a cell's row, column and box, just one candidate is left. Place it. This is the most common move in any solve.

Hidden single

A digit that can go in only one cell of a given row, column or box — even if that cell still shows other candidates. Scan digit by digit through each box to find them.

Intermediate techniques

Naked pair

Two cells in the same unit share the same two candidates (say 3 and 8) and nothing else. Those two digits are locked to those two cells, so you can erase 3 and 8 from every other cell in that unit.

Pointing pair

When a digit's only candidates within a box sit in a single row or column, that digit must come from that box — so you can remove it from the rest of that row or column outside the box.

Advanced techniques

X-Wing

Find a digit that, in two different rows, has only two possible cells — and those cells line up in the same two columns. The digit must take opposite corners of that rectangle, letting you eliminate it from the rest of those two columns. (The same trick works with rows and columns swapped.)

When to slow down

On Hard and Expert boards, progress comes from chains of eliminations rather than single placements. Keep your notes tidy — most "impossible" puzzles crack the moment a stale candidate gets crossed off.

New to the game? Start with the how to play Sudoku guide for the rules and your first moves.