What is Sudoku in simple words?

Sudoku is a logic puzzle played on a 9×9 grid. You fill empty cells with digits 1–9 so that every row, every column and every 3×3 box contains each digit exactly once. There is no arithmetic — only deduction.

What does the word Sudoku mean?

Sudoku is short for the Japanese phrase sūji wa dokushin ni kagiru — roughly “the digits must remain single.” The modern 9×9 form was popularised in Japan in the 1980s and went global in the 2000s. See also our Sudoku meaning page.

Is Sudoku a maths game?

No. Digits are only symbols. You never add or multiply. You could replace 1–9 with nine colours or letters and the puzzle would be identical.

Number-place grids appeared in US puzzle magazines in the late 1970s (notably Dell). Nikoli in Japan named and popularised the modern Sudoku format. Global newspaper fame followed in the early 2000s.

How long does a Sudoku take?

Easy boards often take 3–8 minutes. Medium 5–15. Hard and Expert can take 20–60+ minutes depending on technique skill.

Definition · Rules · Free board

What is Sudoku?

Sudoku is a number-placement logic puzzle. Fill a 9×9 grid so each row, column and 3×3 box contains the digits 1–9 once — no maths required.

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Sudoku in one paragraph

A standard Sudoku starts with some cells already filled (givens). Your job is to complete the rest. A published puzzle should have exactly one solution. On Zeloku, every generated board is uniqueness-checked before you see it.

The three rules

Rows — each of the nine rows contains 1–9 once.
Columns — each of the nine columns contains 1–9 once.
Boxes — each of the nine 3×3 boxes contains 1–9 once.

Full detail: Sudoku rules · Sudoku meaning.

Sizes beyond 9×9

Kids and mini boards use the same logic on smaller grids: 4×4 and 6×6 mini Sudoku and kids Sudoku. Variants like Killer Sudoku add cage sums on top of classic rules.

Why people play

Sudoku trains attention, working memory and pattern recognition in short sessions. It is not a miracle IQ booster — but as a calm daily habit it is hard to beat. See brain-training Sudoku for the evidence-based take.

Next steps

FAQ

What is Sudoku in simple words?: Sudoku is a logic puzzle played on a 9×9 grid. You fill empty cells with digits 1–9 so that every row, every column and every 3×3 box contains each digit exactly once. There is no arithmetic — only deduction.
What does the word Sudoku mean?: Sudoku is short for the Japanese phrase sūji wa dokushin ni kagiru — roughly “the digits must remain single.” The modern 9×9 form was popularised in Japan in the 1980s and went global in the 2000s. See also our Sudoku meaning page.
Is Sudoku a maths game?: No. Digits are only symbols. You never add or multiply. You could replace 1–9 with nine colours or letters and the puzzle would be identical.
Who invented Sudoku?: Number-place grids appeared in US puzzle magazines in the late 1970s (notably Dell). Nikoli in Japan named and popularised the modern Sudoku format. Global newspaper fame followed in the early 2000s.
How long does a Sudoku take?: Easy boards often take 3–8 minutes. Medium 5–15. Hard and Expert can take 20–60+ minutes depending on technique skill.