Installing Obsolete Firefox Extensions
With the new release of Firefox, my friends are once again complaining that all their old extensions don't work. The truth is, they probably actually do work. Unless your extension is something that really plays around with the things like tabs or other really basic behavior which has been changed in the new version, chances are they will still work. The problem is simply that they won't install.
Why not? Simple. Because most extension makers don't want to be accused of effing up your browser when you upgrade, they make their extensions obsolete at each new version of Firefox until they've had a chance to debug them and make sure they don't conflict with your browser. Usually that's fine. But what about that old extension that's no longer maintained? What about the extension whose author takes weeks or months to update?
Well, there is a workaround. You can update the file yourself! It's really quite simple. An extension file is really just a .zipped archive with a .xpi extension. All you have to do is open up the archive, edit a single line in a single text file, save, and voila!
Caution: Proceed at your own risk! Although chances are that your extension will work fine with the new version of Firefox, there are some which do not. You may encounter little bugs or major conflicts. Don't blame me!
Instructions:
1) Download the .xpi file for your obsolete add-on. (I do this by right clicking on the "Add to Firefox" button and choosing "Save link As...")
2) Open the file using your favorite .zip tool. I use 7zip.
3) Extract and open the file install.rdf using your favorite text editor (I used notepad).
4) Find the line that begins
5) Edit that line to read 3.0
6) Save and exit.
7) Replace the file install.rdf in the archive with your edited file. Save and exit.
8) In Firefox, open the updated .xpi file using the File > Open File... comand.
I've done this successfully with Autocopy and LiveJournal Hook. If anyone wants to share any successes or failures, please feel free.