Sudoku
The world's favourite logic puzzle. Fill the grid so every row, column and box holds 1–9. Pencil notes, hints, and mistake checking — across four difficulties. No ads, no sign-in.
Select a square, then pick a number.
Click a square and type a number (or use the pad) · Notes mode adds pencil marks · Arrow keys move.
Like it? Take it offline.
The full Sudoku — with tracked hints, notes and saved best times — is part of Snackpack Brain Games, our calm Android bundle of nine classics.
- Plays fully offline — flights, commutes, anywhere
- Best times & daily streaks saved on your device
- Eight more games in the same app · no ads, no tracking
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How to play Sudoku
Sudoku is played on a 9×9 grid divided into nine 3×3 boxes. A handful of digits are filled in to begin. Your job is to complete the grid so that every row, every column, and every 3×3 box contains each of the digits 1 through 9 exactly once. There's no arithmetic involved — it's pure logic, and every puzzle here has exactly one solution you can reach by reasoning alone.
Click a square and type a number, or tap a number on the pad. Switch on Notes to jot small pencil candidates in a square while you narrow things down. Check highlights any wrong entries, and Hint fills the selected square correctly when you're stuck.
Strategy tips
- Scan for singles. Look for a square where only one digit can possibly go — either because the row, column and box rule it out (a "naked single") or because a digit fits only one spot in a unit (a "hidden single").
- Pencil in candidates. Use Notes to mark every possible digit per square; the puzzle solves itself as candidates disappear.
- Work the most-filled units first. Rows, columns and boxes that already have many digits give you the quickest deductions.
- Look for pairs. If two squares in a unit can only hold the same two digits, those digits can be removed from every other square in that unit.
- Never guess. If you're tempted to guess, there's a logical step you've missed — slow down and scan again.
A little history
Although it feels timeless, modern Sudoku was designed by Howard Garns, a retired American architect, and first published in 1979 as "Number Place." It was popularised in Japan in the 1980s under the name Sudoku ("single number"), and exploded worldwide in 2004–2005 when newspapers began printing a daily puzzle. Today it's one of the most-played logic puzzles on earth — and unlike a crossword, it needs no language at all.
Frequently asked questions
Is this Sudoku free?
Yes — it plays free in your browser with no ads, no sign-in, and nothing to install.
Does every puzzle have a unique solution?
Yes. Each board is generated and verified to have exactly one solution reachable by logic.
How do pencil notes work?
Tap “Notes” to switch into note mode, then enter digits to add or remove small candidate marks in the selected square.
Can I play offline?
The web version needs an open browser tab. For fully offline play with saved best times, install the free Snackpack Brain Games app on Android.