The biggest handicap about using Firefox 3.5 right now is the lack of availability of some of our most loved addons.Yes they are being migrated to 3.5 fast, but yet why wait for them, when you can use them right away? Yup! With a little hack, you can fool your Firefox to believe that the addon is applicable to the version 3.5. However, this might lead to some performance issues.

Ok, so let’s start. I am using one of my most used addon as an example – YSlow (You can also check our recommended list of addons for Developers).YSlow is a wonderful addon for your webpage optimisation and I sorely miss it in 3.5 as its not migrated yet. Let’s Begin.

What you should know first of all is that the .XPI file for all addons is actually a compressed ZIP file. So, if you use an archiving program to extract an XPI file, you’d get a lot of config files for the addon.

So, first of all let us download the latest available version of YSlow (version 2.0.0b3 released on April 29, 2009). Download it, don’t install it. If you have trouble downloading the file with Firefox, better use some other non-gecko/mozilla browser like IE, Chrome, Opera, and Safari.

Now open the file with an archiving program. For the sake of ease, you might also want to rename the XPI into ZIP. Extract the files from the archive now. Look for install.rdf now and open it in a text editor. The RDF is an XML file. You will see the following block:

<RDF:Description RDF:about="rdf:#$41y0G2"
                   em:maxVersion="3.0.*" />

Simply change the em:maxVersion value to 3.5 or 4 if you please. Save the file. Compress all the files back into a ZIP archive. Rename to XPI. Open with & Install on Firefox 3.5 and you are done.

Remember, even though you have fooled Firefox 3.5 in believing that the addon is applicable to the version, however you have not modified the addon codebase. So, it will still use the older objects and elements present in previous versions and not use Firefox 3.5 to its best potential, and/or not perform properly. So do upgrade to the official 3.5 version of the addon as soon as it is released.

Have Fun!

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