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Originally, ff3sudoku was a Firefox 3 add-on for playing SUDOKU. Now it also features a stand-alone application and a Google Chrome extension.The main goals of the project are:
  • To play sudokus from various web pages.
  • To stay simple yet powerful.
  • And one more small goal: to be the best javascript sudoku engine out there.

Current version: 1.1.0


Firefox Extension

ff3sudoku requires Firefox 3 or newer. Works very fine with FF3.1 betas. You can install it from

Google Chrome Extension

Firstly, follow this post to get the development branch of Google Chrome and to enable extensions.There is no need you make your own extension, just make sure you run Google Chrome with parameter:
Then click this link to install the ff3sudoku extension. You will be asked whether you really want to do it. After you have installed, there will be 2 features available to you:
  1. A sudoku icon on your bookmark toolbar. When you click it, a new SUDOKU puzzle opens.
  2. When you visit, there will be a link, in the top-left corner of the screen, which will allow you play the websudoku puzzle in ff3sudoku.
Google Chrome does not allow extensions to store any data yet. Therefore you will loose any unfinished puzzles. Pitty I cannot use Google Gears.

Play online

Online version of my sudoku engine works well in Firefox and Google Chrome. It almost works in Opera. If you have had success in other browsers, please let me know...
Hot news: The online version supports Google Gears. If you have Google Gears installed on your machine, you ff3sudoku will remember your unfinished games.

Looking for hosting

As Google Pages, which now host the on-line version of ff3sudoku, are going to be shut down, I am looking for some other hosting that will allow html, css and javascripts, and that will not place ads in my pages. If you have got any suggestions, please let me know at


This video contains instructions on how to use the extension.


After the installation, you can display the SUDOKU sidebar, either by pressing Ctrl+Shift+S, or from menu View->Sidebar->Your SUDOKUs. The sidebar contains all the SUDOKUs you have started to play and not yet finished. It also contains 2 buttons to start a new medium or hard puzzle. This part still needs some work, because the button for starting a hard puzzles often generates a medium puzzle. 

The button Play! can also be middle-clicked to open the puzzle in a new tab.


The add-on can detect SUDOKUs on some web-pages. If that happens, a notification is shown.

The add-on can detect puzzles from following sites:

If you know about any other it supports, please let me know. If you wish to add support for some more, let me know as well, I will see what I can do. Post me a note to: mailto://

Let's play

Finally the most important part. As you might have noticed, most of the web SUDOKU engines require you click on the cell and press a key - preferably a number. My approach is much closer to native applications. First, choose the number you want to place, then click on cells to place the number.

The features include:

  • Highlighting of the column and row under the mouse.
  • Highlighting of the number being placed.
  • Highlighting of mistakes.
  • Marking of the used-up numbers.
  • Placing hints.

Some tips:

  • You can place/remove hints by middle-click, right-click or ctrl-click. Pick one that does not clash with your browser settings.
  • You can press numbers to select the number to be placed. (see known bugs)
  • Select an eraser by pressing a spacebar or 0.
  • Double-click on a cell to clear it. Double-click also selects the next number to place.

Planned features

  • Add the possibility to define puzzles.

Petr Blahos,
May 9, 2009, 5:15 AM