How to play Sudoku
A practical guide to the objective, legal flow, and decisions that matter in this playable version.
Objective
Sudoku fills a nine-by-nine grid so every row, column, and three-by-three box contains digits one through nine exactly once. Given clues never change; the puzzle is solved entirely through logical placement.
How a turn works
Select an empty cell and choose a digit from the number pad, or use the keyboard. The game rejects a digit already present in that row, column, or box. Use Erase to clear a non-fixed entry. There is no pencil-mark mode in this version: keep candidate notes separately if you need them. An accepted entry is locally legal, not a guarantee that it is the solution.
Strategy that changes the outcome
Begin with units containing many givens. Look for naked singles, where a cell has one candidate, and hidden singles, where a digit has only one possible position within a row, column, or box. Candidate pairs and intersections can then remove possibilities from neighbouring units.
First decision: Use row, column, and box exclusions together; a candidate becomes a placement only when its alternatives have been eliminated.
A common mistake to avoid
A digit that fits the row can still conflict with its column or box. Every committed placement must satisfy all three units simultaneously.
Three useful table habits
- Scan boxes and their crossing rows together.
- Keep candidate notes on paper; the number pad commits a value.
- When stuck, find the digit with the fewest positions in a unit.
A question players ask
Should a Sudoku solution require trial and error?
A well-formed puzzle has one solution and can be progressed by logic. If a guess seems necessary, recheck candidates and interactions; an earlier overlooked single or incorrect note is often the real obstacle.
About this guide
We compare the rules shown in the game with the implemented legal moves, complete representative deals, and review desktop and mobile presentation. If a house rule changes play, the in-game How to play panel takes precedence. Read How games are researched and tested.