How to bypass the Firefox Add-on site's blocking of incompatible extensions for Firefox 3 beta

DISCLAIMER: Please note that I have done this for testing purposes ONLY. I make no claim that this will work with any currently incompatible Firefox extension. Even after installing, you may experience compatibility issues, for which I, nor the extension's author, are responsible. Use at your own risk.

Following-up on my recent adventures with Firefox 3 beta 5, I was wondering how to go about bypassing the incompatibility checking for extensions. One of the nice features of the redesigned Firefox add-ons site is that it automagically shows you if an add-on is compatible, and if so, will allow you to install it. However, at this time most add-ons are not yet compatible, so this is what you see:

This add-on is for older versions of Firefox

This checking process makes perfect sense, and I think is a tremendous bonus for all those using Firefox. However, I still want to work with some of my favorite add-ons, and of course I am willing to accept the inherent risk of doing so.

In the previous iteration of the Firefox Add-ons site, you could still download the .xpi file itself and by using either an extension or editing some behind-the-scenes code, force Firefox to allow installation of the add-on. Unfortunately, with the new site there no longer seems to be an easy way to manually download the add-on since you cannot bypass the site's built-in compatibility checker.

Or is there?

Here's a video tutorial of how I did it

(NOTE: this link will open to a screencast.com video. Unfortunately, Jing doesn't let me resize video, so the dimensions are large. I'm waiting for Vara Software's ScreenFlow app. for OS X to arrive, so hopefully this won't be an issue in the future).

Here are the step-by-step instructions.

1. At the Firefox Add-ons site, download and Install the Nightly Tester Tools 1.3 add-on.
2. Relaunch Firefox.
3. Next, configure the Nightly Tester Tools add-on preferences to disable add-on compatibility checking.
4. Relaunch Firefox.
5. Go back to Firefox Add-ons site.
6. Find your favorite add-on (in my case del.icio.us Complete 1.3).
7. On the add-on's page, right-click anywhere on the page and select View Page Source in the context menu.
8. In the View Page Source window, do a search for "xpi" (w/out quotes), or simply scroll down about halfway until you see something like the following (click to enlarge):





9. Select the URL as highlighted, paste it into the address bar, and prepend it with [ https://addons.mozilla.org ] (without brackets).
10. The end result will be similar to the following URL (depending on the add-on you choose): [ https://addons.mozilla.org/en-US/firefox/downloads/file/8931/del.icio.us_complete-1.3-fx.xpi ] (without brackets).
11. Using this URL, you should now be able to download and install the add-on as usual (the Nightly Tester Tools add-on will help with this).

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