Sudoku

How to play Sudoku

Sudoku is a logic puzzle on a 9×9 grid divided into nine 3×3 boxes. Some cells start filled (the “givens”). Your job is to fill every empty cell with a digit from 1 to 9 such that:

• Each row contains every digit 1–9 exactly once.
• Each column contains every digit 1–9 exactly once.
• Each 3×3 box contains every digit 1–9 exactly once.

Controls

• Tap a number in the palette below the board to select it. The selected number is highlighted in yellow.
• Tap an empty cell to place the selected number there.
• To erase a number you placed, tap the cell first to highlight it, then tap it again (or use the “Erase” button).
• Tap a filled cell (yours or a given) to highlight all peers (same row, column, and box) and all cells with the same digit.
• Givens (the original puzzle numbers) cannot be edited.

Mistakes and the leaderboard

If a placement doesn’t match the solution, it appears in red and counts as a mistake. The mistake counter is shown at the top.

• You can make up to 3 mistakes while still being eligible for the leaderboard.
• From the 4^th mistake onward, the game continues but your time will not be uploaded to the public leaderboard.
• Your local best on this device is also only updated for clean (≤ 3 mistake) wins.

Difficulty levels

• Easy — 40 starting numbers. Most cells are constrained, easy to deduce step by step.
• Medium — 32 starting numbers. Requires more reasoning across the whole board.
• Hard — 26 starting numbers. Sparse; expect to use techniques like X-wing, swordfish, or naked pairs.

Strategy tips

• Look for “singles.” A cell with only one possible digit (because all other 8 are forbidden by row/column/box) is a forced move.
• Scan by digit. Pick a digit (say 7) and look for rows/columns/boxes that don’t have it yet. Often there’s only one place a 7 can go.
• Use the palette counter. The small “{n}/9” under each digit tells you how many of that digit are already correctly placed. Numbers close to 9 are usually easier to finish.
• Don’t guess on Hard. If you can’t see a forced move, look harder for techniques like “naked pairs” (two cells in a unit that can only contain the same two digits).

Offline play

Once this page has loaded, the game runs entirely in your browser. You can keep playing if you go offline. Scores you earn while offline are queued and uploaded automatically when you reconnect (only if logged in and within the 3-mistake limit).