About Sudoku.io

Sudoku.io is a free sudoku game that runs directly in your browser. It was built by Henke Games Studios, an independent one-person studio, as a take on sudoku that keeps the classic logic puzzle intact while adding the pacing and scoring of an arcade game.

What Makes It Different

Most sudoku sites present the puzzle and little else. Sudoku.io adds a scoring layer on top of the traditional game: correct answers chain into a combo multiplier that decays if you take too long, so there's a real trade-off between careful deduction and keeping your streak alive. Mistakes cost a life, which means reckless guessing is punished the way it should be.

The result plays differently from a paper sudoku. On paper you can take an hour over a grid; here a clean, confident solve is worth dramatically more than a slow one, which rewards actually learning the solving techniques rather than brute-forcing your way through.

Features

• Four difficulty levels: Easy, Medium, Hard and Extra Hard, each with its own clue count and point values.
• A combo system that rewards accurate, uninterrupted play.
• One hint per puzzle, which reveals the correct digit for your selected cell without awarding points for it.
• A tutorial mode for players who are new to sudoku.
• A neon dark theme, with optional board glow effects and a light mode, all toggleable in the settings menu.
• Local high score tracking — your best score is remembered on your own device between visits.
• Works on desktop and mobile browsers, with keyboard input on desktop.

How the Puzzles Are Made

Every puzzle is generated fresh rather than drawn from a fixed library, so you won't run into the same grid twice. The generator starts from a complete, valid solution and removes digits while verifying at each step that exactly one solution still remains. That guarantee matters: it's what makes it true that you never have to guess. The difficulty setting controls how many clues are left behind when the process stops.

Built With Flutter

The game is written in Dart and built with Flutter, compiled to run in the browser through WebAssembly and CanvasKit. The same codebase also targets Android and iOS, which is why the interface is designed to work equally well with a mouse, a keyboard or a touchscreen.

Privacy and Cost

Sudoku.io is free to play with no account, no sign-up and no download. Your scores and settings are stored locally in your own browser, not on a server. See the privacy policy for full details on what is and isn't collected.

Contact

Bug reports, feature suggestions and general feedback are all welcome. You can reach Henke Games Studios at bo.william.henriksson@gmail.com.