Frequently asked questions
Below are clear answers to common questions. If something is not covered, try our How to Play and Strategies pages, or the leaderboard and difficulty guides.
Is Sudoku Online free?
Yes. You can play unlimited puzzles in the browser at no cost. Creating an account is optional and only needed if you want your scores on the global leaderboard.
Do I need to create an account?
No. Guest play works for the full game. Sign in when you want your results saved to the leaderboard or a smoother experience across devices.
What is the difference between free puzzles and paid downloads?
Free play is endless online Sudoku on the site. Paid packages are curated PDF puzzle packs you download and print or solve offline; they are sold separately through secure checkout.
How does the leaderboard work?
Signed-in players can appear on the global leaderboard. Rankings use your game scores, which depend on difficulty, time, hint usage, and streaks. See the Leaderboard guide for score types and time filters.
Why did my score not appear on the leaderboard?
You must be logged in for scores to save. Network issues or interrupted games can also prevent a save. Finish a puzzle while online and signed in to record a result.
Do hints affect my score?
Yes. Using hints reduces your score multiplier so that cleaner solves rank higher—this keeps competition focused on logical solving rather than unlimited assistance.
What do the difficulty levels mean?
Easy puzzles have more givens and simpler logic; Insane expects harder patterns and longer chains of deduction. See our Difficulty levels page for typical solve times and who each level suits.
Can I play on my phone?
Yes. The site is responsive and supports touch. For best results use a modern browser and a stable connection.
Is there dark mode?
Yes. Use the theme control in the header to switch light, dark, or system preference.
Why do I see ads?
When enabled, display ads help support free hosting and development. You can still play the full game; ads do not gate puzzle access.
How do PDF purchases work?
Choose a package on the Download page, complete checkout with a valid email, and follow the success flow to retrieve your files when they are ready. Details appear at purchase time.
I am stuck on a puzzle. What should I do?
Review our How to Play guide for singles and scanning, then Strategies for pencil marks and getting unstuck. Use notes first; hints are always optional.
Does the site work offline?
The game loads in the browser and needs a connection for a normal session. Printable packs are for offline solving once downloaded.
Which browsers are supported?
Recent versions of Chrome, Firefox, Safari, and Edge. Enable JavaScript. Disable aggressive ad or script blockers if the game fails to load (except where you choose to block ads).
Is my data secure?
Authentication uses industry-standard providers (Firebase). Payments go through our payment processor. Read the Privacy Policy for categories of data and how they are used.
Can I use the site for children or classrooms?
Sudoku is family-friendly logic practice. Teachers and parents should supervise internet use and review our Terms and Privacy pages for suitability in their context.