Since Firefox 3.5 has just come out I noticed that some of my addons were refusing to work with the new version. Having found out that this is generally down to the addon installer file containing version numbers for older versions of Firefox, I decided to embark upon a quest to make some of my older addons work with Firefox. The steps I’ve used are outlined below. However, before you start you’ll need to download and install 7-Zip (a review of this can also be read.) I’ve provided a video below which shows you how to install addons which were written for older Firefox. There’s also written instructions below in case you don’t quite see what’s happening in the video.
1. Download the addon:
Unless you already have the addon saved in your files somewhere, you’ll need to download it again. However, you’ll have to use a different browser to Firefox. This is because Firefox checks to see what version you’re using, and references this against the addon compatibility. You won’t be able to install it from within Firefox if you’ve got a newer version than the addon specifies. Therefore, use something like Internet Explorer or Chrome to download the file.
2. Open the file using 7-Zip
Since that single file contains many other files all hidden away inside a single .jar, you’ll need to open it up using 7-Zip to see the innards. Once it’s downloaded, right-click on it, hover over the item in the context menu which says ‘7-Zip’ then click on ‘Open archive’. A new window will now pop up which lists the files which make up the addon.
3. Open the install file
If the file doesn’t automatically open with Wordpad or Notepad, you will need to instruct it to. Copy the file to somewhere else (the easiest location is your desktop) by right-clicking on the install.rdf file and clicking ‘Copy To’. Choose a location and then click ‘OK’. Now navigate to where you copied the file to, right-click on it, and click ‘Open With’ and choose Wordpad. On XP you will need to click ‘Choose Program’ in the menu which appears. In either XP or Vista, select ‘Wordpad’ and make sure you tick the box which says ‘Always use the selected program to open this kind of file’. Now click ‘OK’. You will now need to go back to your 7-Zip window, and should be able to double-click on the ‘install.rdf’ file to open it. If it doesn’t work, close 7-Zip, and open the file again as outlined in step 1. You can then come back to step 4 below.
4. Edit the install file
We now need to alter the version number in the file so it will let us install it into Firefox. In 7-Zip double-click the ‘install.rdf’ file. It should then open in Wordpad. You now need to scroll down until you see something like below:
You will need to change the second version number to this. You can miss off the final ‘.*’ on 3.5 if you wish to, but it may not work with future updates to version 3.5, eg 3.5.1.
Then save the file and close Wordpad. 7-Zip may pop up a message asking if you want to update the file. Click ‘OK’ to update it.
5. Install into Firefox
Finally we’ve reached the end. First you need to open Firefox, and open the addons window (Tools > Addons). You also need to locate the original location that the addon downloaded to. Ususally a downloads folder or your desktop. This is the single file that you extracted in step one. You need to drag that file over to the addons window. Firefox will then ask you to confirm that you want to install it. Click ‘OK’ and it should do it for you. You’ll then need to restart Firefox for the installation to complete.
I hope that this worked for you! Let me know if you had any trouble getting it to function. If the addon doesn’t work right, you can still disable it in the same way you would any other addon; through the addons window in Firefox.