Sudoku Hints: How to Find Your Next Move Without Guessing
A helpful Sudoku hint should teach you where to look, not steal the satisfaction of finishing the grid. The most reliable hints explain a logical relationship and leave the next decision in your hands.
Start with naked singles
A naked single occurs when a blank square has only one legal candidate. Check the values already used in its row, column, and box. If eight numbers are ruled out, the ninth is the only possible answer.
This is the ideal first hint because it is transparent. You can confirm it yourself and use the same pattern elsewhere.
Then look for hidden singles
A hidden single is different: several squares may be empty, but only one square in a row, column, or box can hold a specific number. Review the candidates for one digit at a time.
When a puzzle becomes harder, a pair of matching candidates can also eliminate choices around them. Treat that as a cue to inspect the unit more closely, not as an automatic answer.