Sudoku Solver Guide

Sudoku is a 9×9 grid split into nine 3×3 boxes. Fill every cell so that each row, each column, and each 3×3 box contains the digits 1–9 exactly once. That single non-repetition rule is the whole game — every technique below is just a faster way to apply it.

A proper Sudoku has exactly one solution and never requires guessing. If you find yourself wanting to guess, there is a logical move you haven’t spotted yet.

Work these in order — most puzzles fall to the first two or three:

• Naked singles — a cell where only one digit is possible. Scan for cells boxed in by their row, column, and box.
• Hidden singles — a digit that can only go in one cell of a row, column, or box, even if that cell could “fit” other digits.
• Naked pairs/triples — two cells in a unit that share the same two candidates lock those digits out of the rest of the unit.
• Pointing pairs — when a digit in a box is confined to one row or column, eliminate it from the rest of that row/column.
• X-Wing and beyond — advanced patterns for the hardest grids, where a digit’s positions across two rows/columns eliminate candidates elsewhere.

The fastest solvers “cross-hatch”: pick a digit, then sweep every box asking where it can legally go given the rows and columns already containing it. Doing this digit-by-digit surfaces hidden singles far faster than examining one empty cell at a time.

Pencil-mark candidates only when scanning stops yielding placements — premature pencil marks slow you down on easy boards.

NYT publishes Easy, Medium, and Hard daily. Easy boards are solvable with naked and hidden singles alone. Medium adds pairs and pointing. Hard boards require chaining several elimination techniques and disciplined candidate tracking — slow down and pencil-mark fully before hunting patterns.

A new set of Sudoku puzzles is released every day.