Sudoku
Play classic Sudoku - fill the 9×9 grid so every row, column and 3×3 box contains 1-9. Four difficulty levels with notes mode.
Play classic Sudoku - fill the 9×9 grid so every row, column and 3×3 box contains 1-9. Four difficulty levels with notes mode.
This free Sudoku from KX Toolkit is part of our all-in-one online toolkit. It runs entirely in your browser, so your data never leaves your device for client-side operations. 100% free, forever - no paywall, no credit card, no trial.
How to use the Sudoku
- Open the tool - you are already here, nothing to install.
- Enter your input in the form above.
- Click the action button to run the tool. Results appear instantly.
- Copy the result to your clipboard, or download it as a file.
What you can do with the Sudoku
- Speed up daily work without juggling multiple websites.
- Run quick checks before publishing or sending.
- Verify or transform data without writing any code.
- Free alternative to paid desktop or SaaS tools.
Why use KX Toolkit's Sudoku
- Browser-based: Works on Windows, macOS, Linux, iOS and Android - no install, no extension.
- Privacy-first: Client-side tools never upload your data; server-side tools delete files right after processing.
- Mobile-friendly: Full feature parity on phones and tablets - not a stripped-down view.
- Fast: Optimised for instant feedback. No artificial waiting screens, no email-gated downloads.
- One hub for everything: 300+ tools across SEO, text, image, PDF, code, color, calculators and more - skip switching between sites.
Tips for the best results
For best results, keep your input as clean as possible - remove extra whitespace or formatting before running the tool.
Related Browser Games
If you find this tool useful, explore the full Browser Games collection or browse our complete tool directory. KX Toolkit is built for marketers, developers, designers, students and anyone who needs a quick utility without signing up for yet another SaaS.
How do I play Sudoku?
Fill the 9x9 grid so that every row, every column and every 3x3 box contains the digits 1 through 9 exactly once. The puzzle starts with some cells already filled in. Click an empty cell and choose a number from the on-screen keypad. The puzzle is solved when every cell is filled and no row, column or box contains a duplicate.
What difficulty levels are offered?
Easy puzzles can be solved with simple scanning of rows, columns and boxes. Medium requires basic candidate elimination techniques. Hard requires more advanced moves like naked pairs, hidden pairs and pointing pairs. Expert puzzles can require X-wing or swordfish patterns. Pick a difficulty from the menu before starting, because changing difficulty mid-puzzle resets the board.
Can I take notes in cells?
Yes. A pencil mark mode lets you place small candidate numbers in any empty cell, just like marking up a paper Sudoku. Tap pencil mode, then tap candidates into a cell. Switch back to normal mode to enter a confirmed answer. Pencil marks are cleared automatically when you place a final answer in that cell, which keeps the grid tidy.
Are mistakes flagged automatically?
A toggle in the menu controls whether duplicate numbers in the same row, column or box are highlighted. With highlighting on, you spot mistakes immediately, which is friendly for beginners. With highlighting off, you must verify your work yourself, which is more like solving a paper puzzle. Many players turn highlighting off once they reach hard difficulty.
Is the puzzle the same every time?
No. Each round generates a fresh puzzle with a single guaranteed solution, so two players starting at the same time face different boards. The generator always produces unique-solution puzzles, which means no guessing is ever needed if you apply correct techniques. Save the page if you want to come back to a particularly enjoyable puzzle later, because progress is saved per device.
Are best times saved?
Yes. Your fastest completion time for each difficulty is stored in browser local storage and shown above the grid. Beating your record triggers a celebration. The current puzzle's elapsed time is shown in real time, and pausing the timer hides the grid to prevent accidental cheating. Clearing browser data resets all best times, so be careful with site data cleanup.
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