ChillSudoku
A new Sudoku puzzle every day, three difficulty levels, no signup. Pencil mode for notes, automatic timer, conflict highlighting. Solve in your browser on any device — phone, tablet, desktop. Free forever.
How to Play Sudoku
Fill the 9×9 grid so every row, every column, and every 3×3 box contains the digits 1 through 9 exactly once. The starting puzzle already has some digits filled in (the "clues"); your job is to figure out the rest.
- Tap a cell to select it. Use number buttons or your keyboard (1–9) to enter a digit.
- If a digit would break the row/column/box rule, it flashes red — backtrack and rethink.
- Use pencil mode (✏️ button or press N) to mark candidate digits in a cell. Useful when you have narrowed a cell down to 2–3 options.
- Arrow keys move the selection. ⌫ (or 0) clears the selected cell.
- Solve every cell correctly to win. The timer shows your solve time.
Difficulty Levels
| Level | Clues | Typical solve time | Best for |
|---|---|---|---|
| Easy | ~40 | 3–8 min | Beginners, quick warm-up, sleepy mornings |
| Medium | ~32 | 8–20 min | Most players. Requires basic scanning + notes. |
| Hard | ~26 | 20–60 min | Veterans who want a real fight. Needs advanced techniques. |
Every puzzle on ChillSudoku is guaranteed to have exactly one solution. No guessing required — every move is logically deducible from the current state of the board.
Solving Strategies
1. Scanning (start here)
Pick a digit (say 5). Look at each 3×3 box and ask: where can the 5 go in this box? Sometimes only one cell is possible. Place it. Move to the next box. After scanning all nine boxes for one digit, move to the next digit.
2. Pencil marks (when scanning stops working)
Switch to notes mode and write the candidate digits in each empty cell. Once you see a cell with only one candidate (or a row/column/box where a candidate appears in only one cell), you can place it confidently.
3. Naked pairs and hidden pairs
If two cells in a row both have exactly the candidates {3, 7} — those two digits must go in those two cells. So remove 3 and 7 from all other cells in that row. This often unlocks chains of new placements.
4. Pointing pairs
If within a 3×3 box, all the candidate cells for a digit lie in the same row (or column), then that digit must go in that box. So remove the candidate from the rest of the row outside the box.
5. When stuck — change direction
Walk away for a minute. Come back. Scan a fresh digit you haven't looked at recently. The eye sees new patterns when you switch context.
Why Sudoku Is Good for You
Sudoku is a workout for working memory and pattern recognition. Daily play builds focus that transfers to other tasks. Unlike scrolling feeds, a Sudoku session leaves you mentally refreshed instead of drained. Five to ten minutes a day is enough.
Frequently Asked Questions
Is ChillSudoku free?
Yes. No signup, no download, no popups. Just open the page and play.
When does the daily puzzle reset?
Midnight UTC. Every player worldwide gets the same puzzle on the same day.
What difficulty levels are there?
Easy (~40 clues), Medium (~32 clues), Hard (~26 clues). Each daily date generates a fresh puzzle at each level — switch any time.
How do pencil marks (notes) work?
Tap the pencil button or press N to toggle notes mode. Tapping a digit then adds it as a small candidate mark in the selected cell. Tap the same digit again to remove it.
Are puzzles guaranteed to have a unique solution?
Yes. The generator removes cells one at a time and verifies a unique solution remains. You will never be stuck guessing.
Can I share my time?
Yes. After solving, a Share button copies a short text with your time and difficulty.
Does my progress save if I close the tab?
Yes. Your in-progress daily puzzle saves locally and reloads automatically — until the next day rolls over.
Why is conflict highlighting on by default?
Because the goal is a calm, satisfying solve — not memorizing the rules. If a digit you place would violate row/column/box rules, it flashes red. You can still enter it; it just helps you spot mistakes early.
About
ChillSudoku is built by people who like calm puzzle play without ads in the face. More about the project, or email hello@chillsudoku.com.