Firefox 4 Extensions Support Change Could Lead to More Compatibility Issues

Mozilla has just announced a small change that could have a big impact for Firefox extension developers. Specifically, the upcoming Firefox 4 beta will no longer unpack the XPI archive in which extensions are distributed, rather, it will read all of the files from inside the archive.

"The next beta of Firefox 4 will include a change to how Firefox installs and uses extensions," an entry on the Mozilla add-ons blog read.

"Previously the files from the extension’s XPI would be extracted into their own directory in the filesystem and read from there, now the default is to just keep the XPI and load files out of it directly," it explained.

"For many extensions this causes no problems however if your extension’s code tries to access its files directly or if your extension includes binary code, search plugins, dictionaries or window icons then you may either need to make changes to your extension," it warned.

Mozilla says that the change should be transparent for many extensions out there. However, for some, the change will lead to problems so Mozilla urges devs to adapt their creations.

Developers have two ways of coping with the changes. On the one hand, they can make the necessary changes to their extensions so that they don't access files directly. At the same time, they can just ask Firefox to unpack the extension anyway to ensure that it works as intended.

This latter option is somewhat of a hack, but it can be used to ensure compatibility quickly, though, it's probably recommended to implement the changes properly, by modifying the extension code.

The announcement only concerns developers, the users will not notice any difference from the way Firefox handles extensions. Of course, they will notice if their favorite extension suddenly stop working, but, hopefully, developers will get right on it implementing the changes.