PIENSALIA / SUDOKU EDUCATION
Naked Singles in Sudoku
A Naked Single is a cell with exactly one legal candidate after its row, column, and box are checked.
Level: Learn how Naked Singles work in Sudoku, how to find them, and how to avoid common candidate and placement mistakes.
Prerequisites
Know the three Sudoku rules and keep candidates consistent across each row, column, and 3 × 3 box.
How to apply it
- Scan the relevant units and write only legal candidates.
- Compare the positions or candidates described by the technique.
- Make one justified placement or elimination.
- Update related notes and rescan for new singles.
Worked example
A cell blocked by 1, 3, 4, 6, 7, 8, and 9 must contain 2. The placement is certain because the candidate list has one value.
Common mistakes
- Guessing before checking every related unit.
- Leaving stale candidates after a placement.
- Applying a pattern without verifying all of its positions.
When to use it
Use Naked Singles during the opening scan and after every confirmed placement.
Practice Sudoku
Apply this technique in a free puzzle without an account.