Sudoku is a free daily number puzzle where you fill a 9×9 grid so that every row, column, and 3×3 box contains the digits 1 through 9. Each day brings a fresh puzzle at four difficulty levels — Easy, Medium, Hard, and Expert — all generated uniquely by a seeded algorithm so every player worldwide sees the same daily challenge. If you enjoy sudoku puzzles online, Sudoku offers the same satisfying logic experience you know and love — but with zero ads, zero tracking, and no account required. Unlike many popular sudoku sites cluttered with banners and pop-ups, Sudoku is completely free and works offline as a Progressive Web App. It's one of the cleanest free sudoku experiences available anywhere. Sudoku includes pencil-mark notes, conflict highlighting, undo/redo, and a hint system — everything you need to solve even the toughest Expert grids.
Fill every empty cell in the 9×9 grid with a digit from 1 to 9. The rules are simple: each row must contain the digits 1–9 with no repeats, each column must contain the digits 1–9 with no repeats, and each of the nine 3×3 boxes must also contain the digits 1–9 with no repeats. Select a cell by clicking or tapping it, then press a number key or tap the number pad to fill it in. Conflict cells are highlighted in red — use these as clues that something needs to change. Enable Notes Mode (pencil icon) to jot down candidate digits without committing to an answer. Use Undo/Redo to backtrack, and Hint (up to 3 per game) when you get stuck.
Look for naked singles first — cells where only one digit is mathematically possible given the current row, column, and box. These are your fastest early wins. On Medium difficulty, add hidden singles to your toolkit: scan each row, column, and box for a digit that can only fit in one cell within that unit, even if that cell has multiple candidates. For Hard and Expert grids, switch on Notes mode and pencil in all candidates for every empty cell before solving — don't rely on memory. When you place a confirmed digit, immediately remove it from the notes of every cell in the same row, column, and box. If two cells in a unit share the exact same two candidates and no others, those digits are locked there — eliminate them from every other cell in that unit.
Many popular sudoku websites are loaded with intrusive ads, paywalls, or require you to create an account. Sudoku takes a different approach: it's a free sudoku no ads experience, built as a privacy-first Progressive Web App. Your progress is saved locally — nothing is ever sent to a server. You can even install it on your phone and play sudoku offline without an internet connection. Compared to ad-heavy sudoku sites, Sudoku loads faster, works offline, and never shows banners or pop-ups. All four difficulty levels — including Expert — are available for free, every single day.
Sudoku on PuzzleBoxs is the cleanest free sudoku experience on the web. No ads, no tracking, no account required — your progress is saved locally and never leaves your device. All four difficulty levels (Easy through Expert) are available every day at no cost. Install Sudoku as a Progressive Web App and play offline on your commute or a flight. The built-in tools — notes mode for candidate tracking, conflict highlighting to catch mistakes, undo/redo for backtracking, and hints when you're truly stuck — give you everything you need to solve even the toughest Expert grids without frustration.
Yes, Sudoku is 100% free with no paywalls, subscriptions, or ads — ever. All four difficulty levels (Easy, Medium, Hard, Expert) are available for free every day.
No. Sudoku runs entirely in your browser. We use no cookies, no analytics scripts, and no advertising SDKs. All your game data — statistics, progress, settings — is stored locally on your device and never sent to any server. This makes Sudoku one of the most privacy-friendly free sudoku games available.
Yes! Sudoku is a Progressive Web App (PWA). After your first visit, you can install it on your phone or desktop and play sudoku offline without any internet connection. Your progress is saved automatically.
Tap the pencil/Notes button to enable Notes Mode. In this mode, tapping a number adds a small candidate digit to the cell instead of filling it in. This lets you track possible values while you work through the logic. Notes are automatically cleared when you fill in a confirmed digit.
Easy puzzles have 40 empty cells and can typically be solved using simple scanning techniques. Medium (48 empty cells) requires some elimination logic. Hard (54 empty) demands more advanced techniques. Expert (58 empty) uses minimal clues and tests your full sudoku strategy. Every difficulty has a unique daily puzzle.
Yes! Sudoku uses a date-based seed so every player worldwide sees the same daily puzzle for each difficulty level. You can compare solve times with friends. If you want more puzzles, use the difficulty selector to start a fresh challenge.
Sudoku is a 9×9 number puzzle. You must fill every cell with a digit from 1–9 so that: (1) each row contains the digits 1–9 with no repeats, (2) each column contains the digits 1–9 with no repeats, and (3) each of the nine 3×3 boxes contains the digits 1–9 with no repeats. No math is required — it's pure logic!