Sudoku Studio
Sudoku Studio is a free browser sudoku with a daily puzzle and unlimited practice boards in three difficulties (easy ~40 clues, medium ~32, hard ~27). Every board is generated with a built-in solver so it always has exactly one solution, the daily board is identical for every player worldwide (midnight-UTC reset), and the interface includes pencil-mark notes, undo and an on-demand mistake check. No download, no signup.
Classic rules, honest boards: every puzzle here is verified to have a single unique solution before you ever see it, so you never need to guess. Warm up on easy, settle into medium, or bring coffee for hard.
Generating today’s board…
How to play
- Tap a cell to select it, then tap a number on the pad (or press 1–9) to fill it. Tapping the same number again clears the cell.
- Toggle ✏️ Notes (or press N) to write small candidate numbers in a cell instead of a final answer.
- Clashing digits in the same row, column or box get a gentle highlight the moment they appear — that is a conflict, not a verdict.
- Use Check whenever you want a real audit: cells that contradict the actual solution are marked, and your check-count is part of your result. Fill all 81 cells correctly to win.
Rules
- Fill the 9×9 grid so every row, every column and every 3×3 box contains the digits 1–9 exactly once.
- Given (pre-filled) cells are fixed and cannot be changed.
- Every board — daily or practice — is machine-verified to have exactly one solution.
- The daily board resets at midnight UTC and is the same for every player; the last two weeks stay available in the archive picker.
- Checks are unlimited but counted; a no-check solve is the cleanest result.
Scoring & streaks
Your result is your solve time plus how many checks you used — there is no point system to grind. Solving any daily board on its real day (any difficulty) extends your on-device streak; practice boards never affect it.
Strategy tips
- Start with scanning: pick a digit that already appears often and trace which row/column/box combinations leave only one legal cell for it.
- Hunt naked singles — cells whose candidates have collapsed to one value. Fresh boards usually hide several.
- Then hidden singles: a digit that fits only one cell within a row, column or box, even if that cell has other candidates.
- On medium and hard, keep notes religiously. Pairs of cells sharing the same two candidates (naked pairs) let you erase those digits from the rest of the unit.
- Stuck? Re-scan the most crowded 3×3 box instead of staring at empty space — constraints live where the clues cluster. Guessing is never required on a unique board.
Difficulty
Easy (~40 clues) solves with scanning and singles in a few minutes. Medium (~32) expects notes and hidden singles. Hard (~27) leans on pairs and patient elimination — expect 15 minutes or more. The generator holds these clue bands for every board, daily or practice.
Controls
- Mouse or touch: tap to select, tap the pad to fill; Erase clears, Undo steps back any number of moves.
- Keyboard: arrow keys move the selection, 1–9 fill, Backspace erases, N toggles notes.
- The picker above the grid switches between the last two weeks of dailies and unlimited practice boards; the difficulty selector works in both modes.
Accessibility
Every cell and key is a real button with a descriptive label (row, column, value, given-status), so screen-reader and keyboard play work end-to-end. Selection, conflicts and check-marks all pair color with text or structure, and the grid keeps readable contrast in light and dark themes without horizontal scrolling on phones.
Frequently asked questions
Is the daily sudoku the same for everyone?
Yes. The daily board is derived deterministically from the date for each difficulty, so every player worldwide gets the identical puzzle at midnight UTC.
Are the puzzles guaranteed to have one solution?
Yes. The generator removes clues only while a built-in solver confirms the board still has exactly one solution, so logic alone is always enough — guessing is never required.
What's the difference between the conflict highlight and Check?
The conflict highlight only shows digits that clash with each other right now — it is free and automatic. Check compares your entries against the actual solution and marks wrong cells; it is unlimited but counted in your result.
Do practice boards affect my streak?
No. Streaks only grow from solving a daily board on its real day. Practice is an endless, pressure-free supply.
Can I finish a puzzle later?
Yes — your grid, notes, timer and check-count are stored in your browser per board, so you can leave and resume any time on the same device.
Does it work offline?
Once the page is loaded, generation and play run entirely in your browser — you only need a connection to load the page.