About the game
Sudoku is the world's favourite logic puzzle: a 9x9 grid divided into nine 3x3 boxes, where every row, every column and every box must contain the digits 1 through 9 exactly once. There is no arithmetic involved — only deduction. Each puzzle here is generated with a guaranteed unique solution, which means every single cell can be reached by pure logic. If you ever feel forced to guess, there is always a chain of reasoning you have not found yet.
This version offers three difficulties — Easy (40 clues), Medium (32) and Hard (26) — plus a Daily puzzle that is the same for everyone on the same date. Tap a cell and the grid highlights its row, column and box, plus every cell holding the same digit, so you can scan for conflicts at a glance. Wrong entries turn red immediately. A pencil-notes mode lets you record candidates in a cell before committing, and your fastest solve time is stored per difficulty on your device.
How to play
- Tap a cell to select it, then tap a number on the pad (or press 1–9 on a keyboard).
- Tap the same number again to clear it, or use the ⌫ erase key.
- Toggle ✎ Notes to jot small candidate digits in empty cells; entering a real digit clears that cell's notes.
- Move the selection with the arrow keys; N toggles notes mode.
- Digits you have placed nine times are dimmed on the pad.
Rules
- Every row must contain 1–9 with no repeats.
- Every column must contain 1–9 with no repeats.
- Every 3x3 box must contain 1–9 with no repeats.
- The starting clues are fixed and cannot be changed.
- The puzzle is complete when all 81 cells are filled without conflicts.
Strategy & tips
Scan for singles first
The fastest progress comes from cells with only one possible digit. Pick a number that already appears often, and trace which rows and columns it rules out — where only one empty cell in a box remains, that placement is forced. Sweep the grid this way after every few entries.
Use notes on the hard levels
From Medium up, keeping candidates in your head becomes error-prone. Write two- or three-candidate notes in the tricky cells; when one of them appears elsewhere in the row, column or box, prune it. The moment a cell drops to a single note, it becomes a solved cell.
Look for locked pairs
When two cells in the same unit hold exactly the same two candidates, those digits are locked to that pair — every other cell in the unit can drop them. This single pattern cracks most Hard puzzles wide open.
Let the highlight work for you
Selecting a cell lights up everything it "sees", and selecting a digit shows all its copies. Before placing a number, glance at the highlighted cells: if the digit already appears among them, you have caught the mistake before it happened.
FAQ
Does every puzzle really have exactly one solution?
Yes. The generator removes clues only while a solver confirms the puzzle still has a single solution, so logic alone is always enough — guessing is never required.
What is different about the Daily puzzle?
The Daily is seeded by the date, so everyone in the world gets the same Medium-difficulty grid that day. It counts toward the daily missions on the home page.
Are wrong entries corrected automatically?
No — a conflicting digit just turns red. It marks direct rule violations (a duplicate in a row, column or box), not deviations from the final solution, so an entry can look valid and still be wrong. Red is a fact; white is not a promise.
Is my solve time saved?
Your fastest time per difficulty is stored in your browser's local storage, on your device only. You can also submit a best time to the public leaderboard under a nickname if you choose.
