Ceedoku is a free, lightweight Sudoku game designed to provide a simple and powerful Sudoku experience without unnecessary distractions.
Ceedoku runs directly in your web browser and can also be installed as an app for offline use.
Ceedoku is a Sudoku game built with the goal of keeping Sudoku simple.
There are no advertisements interrupting gameplay, and the game provides a range of features while remaining lightweight enough to run on a wide range of devices.
Whether you want to play a quick Sudoku puzzle or work through one of the harder difficulty levels, Ceedoku is designed to stay out of the way and let you play.
Ceedoku includes eight difficulty levels:
- Easy
- Medium
- Hard
- Expert
- Master
- Extreme
- Impossible
- Godlike
Each difficulty provides a different challenge, with Godlike being the most restrictive difficulty.
Ceedoku includes several tools to help with solving puzzles:
- Pencil mode
- Erase mode
- Undo
- Redo
- Hints
These tools can be enabled or disabled through the settings.
Ceedoku can save your current game so you can leave and return to it later.
The save system stores things such as:
- The puzzle
- The solution
- Entered numbers
- Pencil notes
- Selected cell
- Difficulty
- Timer
- Mistakes
- Undo and redo history
- Game state
Ceedoku also has its own save-file format, Ceedoku Save Format (.csf), which can be used to export and import saves.
Ceedoku supports both:
- Dark mode
- Light mode
The interface is designed to adapt to different screen sizes, including desktop and mobile devices.
Ceedoku also includes:
- Keyboard controls
- Arrow-key cell navigation
- Arrow-key wraparound
- Animations
- Sound effects
- Haptics
- Hint cooldowns
- Offline support
- Responsive layouts
Ceedoku does not include advertisements.
The goal is to keep the game focused on Sudoku instead of filling the interface with advertisements or other distractions.
Ceedoku can be played in several ways.
Note
Ceedoku does not have to be installed to use
Ceedoku can be accessed and used simply by going to the website, or by downloading the latest version from the GitHub Releases Page if you want a local copy of the game.
No installation is required to play this website version.
If you would like to install Ceedoku, the two methods of doing so are below:
Supported browsers can install the website as an application, allowing Ceedoku to appear like a normal app on your device.
A tutorial on how to do that can be found here.
Ceedoku has a desktop version packaged as an executable application.
The desktop application supports Linux, macOS and Windows 10+ across every major architecture (Type of CPU).
Installers for the Ceedoku desktop can be found here
The benefits of using the desktop application to play Ceedoku include:
- The Ceedoku Save Format (
.csf) file extension will be given a nice, beautiful icon, so that you can identify it quickly. - Files ending in Ceedoku Save Format (
.csf) will have their file type show as "Ceedoku Save File" for easier identification. - Ceedoku Save Format (
.csf) files can be opened directly into the app using a double click, and upon doing so will import the save file.
Important
Your OS may warn you that the app could be malicious.
This warning is primarily because the application is not code-signed. Please note that an unsigned application can trigger security warnings even when it is not malicious. Code signing certificates also cost money, and maybe - just maybe - some people don't want to spend upwards of $1000 on one.
Once installed, Ceedoku can be used without an internet connection.
The application keeps the required files locally so that the game can continue working when the device is offline.
Ceedoku uses its own save format:
.csf
Ceedoku Save Format is designed specifically for Ceedoku save data.
The format includes validation data so that invalid or damaged save files can be detected.
More information about the format can be found in the CSF specification:
https://ceedoku.github.io/csfspec/
Ceedoku is primarily a web application.
The game interface is built using standard web technologies:
- HTML
- CSS
- JavaScript
Puzzle generation is handled by JavaScript, with puzzle generation capable of being moved into a Web Worker so that generating difficult puzzles does not unnecessarily block the interface.
The game also uses browser storage for things such as saved games and best times.
The repository contains the source code used to build and run Ceedoku.
Some of the important parts of the project include:
- The main game interface
- Sudoku generation and solving logic
- Save and load functionality
- Settings
- Keyboard controls
- Animations
- Audio and haptic features
- Service-worker/offline functionality
- CSF save-file support
This repository is primarily a static web app. The main languages used are:
- JavaScript: 65.67%
- CSS: 27.20%
- HTML: 7.13%
If you'd like to contribute to Ceedoku, please read the contributing guidelines before submitting a change.
See CONTRIBUTING.md for information about contributing to the project.
These instructions will get a local copy of the project running for development and testing.
Prerequisites:
- A modern web browser (Chrome, Firefox, Safari, Edge)
- Git (to clone the repository)
- Optional: Python 3 or Node.js if you want a simple local static server
Clone the repository:
git clone https://github.com/Ceebug/Ceedoku.git
cd CeedokuOpen in a browser (quick, no server):
- Double-click
index.htmlor open it from your browser's File > Open menu.
Recommended (runs a local static server so Service Worker and fetches behave properly):
- With Python 3:
python3 -m http.server 8000
# then open http://localhost:8000 in your browser- With Node (http-server):
npx http-server -p 8000
# then open http://localhost:8000Development notes:
- This is a static web project — there is no build step by default. Edit the HTML/CSS/JS files and reload the browser to see changes.
- Service Worker caching can serve stale files while developing. To avoid this:
- Open DevTools → Application → Service Workers and unregister the service worker, or
- Use a private/incognito window, or
- Use DevTools → Application → Clear storage and then hard reload (Ctrl/Cmd+Shift+R).
- The game loads local dependency files such as
fsj.jsandjsf.jsfrom the repo root. Ensure those files are present when testing locally.
Contributing:
If you'd like to contribute:
- Fork the repo, create a branch, make changes, and open a pull request.
- Keep changes small and focused. If you're changing UI behavior, explain the motivation in the PR description.
- If adding new code that must be loaded at runtime, test the change with the local server so the Service Worker won't interfere.
Ceedoku is developed primarily using HTML, CSS, and JavaScript.
To work on Ceedoku, clone the repository and open the project in your preferred development environment.
Because Ceedoku is a web application, most development can be tested directly in a modern web browser.
The official Ceedoku website homepage is:
https://ceedoku.github.io/home
The website contains information about the game, installation instructions, downloads, the changelog, and other project information.
Note
https://ceedoku.github.io is the direct link to play Ceedoku.
It does not open the website homepage.
Changes between Ceedoku versions are documented in the changelog:
https://ceedoku.github.io/changelog
The current version is displayed on the Ceedoku website and in the project's release information.
For the latest release, see the GitHub releases page:
https://github.com/ceebug/ceedoku/releases
Ceedoku is actively developed and may continue to receive new features, improvements, and bug fixes.
The project is still evolving, so some parts of the application may change between releases.
Ceedoku — Sudoku, without the nonsense.