Installing free and orphaned extensions to Debian Iceweasel and GNU IceCat

In part, this also applies to Mozilla Firefox.

Debian Iceweasel and GNU IceCat are browsers code-compatible with Mozilla Firefox. For those not in the know, they are both like Firefox, but rebranded, just as some shops order produce from a producer (whether or not they produce generic or their own brand-name products), and the shops then rebrand said produce as "their own". The reason with Mozilla Firefox is that it's a registered trademark that belongs to Mozilla.

There are a number of free extensions and themes for which their publishers don't have their own home pages anymore, and download links from the Internet Archive might not work for various reasons (the most common being that the files were not captured into the vault). These add-ons are generally available from addons.mozilla.org, but the site tends to shut out Debian Iceweasel and GNU IceCat.

Granted, some large Linux distributions have their own repositories that host compatible addons for a specific distro version's specific version of Firefox, but distribution maintainers move on, and repositories that cater for older distros with older Firefox versions are EOL'd, as repos have to host files for newer distro releases.

So, here I had a curious case with Go Green, an MPL-licensed theme for which there was no home page anymore, archive.org didn't host the theme's installer, and the only available place is addons.mozilla.org.

There are two ways to fetch the add-on from Mozilla:

One is the easy way, the other way is more complicated, but also
offers more choice.

The ostensibly user-friendly way to installed the latest version of an add-on is thus_

In the instance of the Go Green theme, you can go to

https://addons.mozilla.org/en-US/firefox/addon/go-green/

— in which page there are two obstacles: One is that all of mozilla.org always uses the latest Cascading Style Sheets (CSS) in formatting its pages, and so the older a version of Firefox is, the less able it is in rendering the pages. Fortunately, Firefox has this great option to view the page without CSS (Cascading Style Sheets).

The other is that JavaScript also blocks showing some links, even if the browser is modern.

So, choose to view the page with no styles:

View > Page Style > No Style

In this case, links and elements previously hidden with CSS will be displayed.

Then, to fetch a specific version of an extension, go to see "Complete version history" (you can jump to it using the text find function; link is clickable).

You should reach this address —

https://addons.mozilla.org/en-US/firefox/addon/go-green/versions/

Or, if you know the address of the add-on, just add versions/ to the URL to see all versions of an add-on, page by page (much simpler, I might add).

The All Versions page shows which browser versions the extension is compatible with, so the best bet is to choose the latest version of the extension that is good for a browser version that matches the prescribed version span.

At the section of a desired extension version, there's a "Continue to Download" link. The link is not clickable, but you can drag it into a new tab, or into the existing tab's widget to cause Firefox to resolve the URL.

In the Go Green theme's case, this will actually open the "roadblock" page, with this address for the page:

https://addons.mozilla.org/en-US/firefox/addon/go-green/contribute/roadblock/?src=search&version=1.25

Since you're using IceWeasel or IceCat, you might still be shut out by JavaScript from downloading an extension, with no download button in sight. This is reasonable, as some extensions won't work in Linux, but the script at mozilla.org is not always able to tell exactly that the user is actually running a compatible browser.

When installing extensions made for an operating system different than Linux, then install these at your own risk. It may be easier with themes, but some complex extensions require that you only install the one made for your operating system, especially if it's also been made available for the OS. I've seen this happen with the DOM Inspector extension, which is made by Mozilla, has been included with Firefox, and is specifically tailored to each specific version of Firefox.

As the roadblock page doesn't show the download link when CSS for it is active, choose to use no styles in the page (if you have so far been dragging the links into the tab widget, then the no styles setting for the tab persists)...

The "Download for Windows" link is placed at its coded position, but is not clickable (probably governed so by JavaScript), so drag it into a new tab and save the extension, or if it's already an xpi, install it.

If the add-on installer's filename has a .jar extension, then the extension can be saved as .xpi or renamed later.

This whole option is then simpler, but might not guarantee that you will be getting the right extension that is made for a browser running in your operating system.

With the Go Green case, the theme has only been made for Windows, but if the browser is compatible, it can also be installed in Linux and for Debian Iceweasel. Case in point:

Click for a bigger image.

Downloading the add-on by name from the Mozilla FTP site

To see if a Linux (or Mac) version of the extension is available, you need to find out the add-on's number at mozilla.org. In some cases it's available already in the extension URL, but I think this nomenclature is being phased out from the web front-end.

If you still don't know what's the number of the addon (if the add-on's address is named and not numbered), you can find it out through its add-on icon or other clues, like links and such. See

View > Page Info > Media

Look for an image, the URL of which matches

/addon_icons/

In that URL, the image's filename starts with a number, like

/13551-64.png

^ 13551 is the number of the add-on (64 is probably the native image width). After that, it's easy to find the add-on via mozilla.org's FTP site:

ftp://ftp.mozilla.org/pub/mozilla.org/addons/13551/

The FTP folder there will then display a list of all release versions of extension or theme installers, which are usually JAR or XPI files. If the installer is a JAR file, and you want to install it for Firefox or Iceweasel, download the extension's installer, rename its extension from .jar to .xpi — and then install it in the browser from the directory it's located in.

And to top it off,

The URL for the Go Green theme's latest installer is this:

http://releases.mozilla.org/pub/mozilla.org/addons/13551/go_green-1.25-fx-win.jar