Novell Moonlight Is In A Lunar Eclipse

It is not often that I stumble upon a website that uses Microsoft Silverlight. I am sure there are thousands of websites that use this technology. I am aware that Netflix uses Silverlight heavily. Still, I think it is safe to say, that Silverlight is not as commonly used as Adobe Flash. So what happens when I actually find my browser at a site that uses it?

Nothing happens. That is for sure.

The page asks me to download the Silverlight browser plugin. Which I obediently did. Unfortunately for us Ubuntu users Silverlight does not support the Linux platform. Well, not directly anyway. Interestingly enough the Microsoft Silverlight browser plugin download page is kind enough to point me to a solution.

Here is where the Novell Moonlight project comes in.

Moonlight to put it simply is, by virtue of Microsoft’s blessing (the redirect), the official browser plugin for Linux users who want to run Silverlight-enabled websites.

Actually, to put it more accurately:

Moonlight is an open source implementation of Microsoft Silverlight for Unix systems. With Moonlight you can access videos, applications and content created for Silverlight on Linux

As I have installed Moonlight before on my desktop I was confident enough that nothing will go wrong with the install. Well surprise, surprise. It turns out the Firefox version I have on my notebook is not compatible with the plugin. I have the latest installed which is 6.0.2 and on my desktop it was only 4 something. Now why had I not anticipated this?

I wondered too. How could the download page not have detected my browser version instead and stopped me from downloading the plugin? That could have saved me, and many others, the trouble of downloading the plugin only to find out later on that is is not even compatible with the Firefox Iā€™m using. A line of code could have solved that easily.

All was not their fault. I was careless enough not to read the FAQ which was prominently displayed at the top of the download page. It said:

Moonlight should work on any modern 32bit and 64bit Linux distributions under Firefox versions 3.0 through 4.x, as well as Google Chrome, from both stable and dev channels

And there we have it. It is too bad I cannot view web pages that use Silverlight. Not my loss but it would have been nice if the plugin just worked.

The Solution

Searching for some answers on the net, there were 2 possible solutions that I found:

  1. Install the Add-on Compatility Reporter
  2. Manually editing the compatibility version of the plugin

#1 somehow did not do the trick for me.

#2 on the other hand was a success!

On how to do #2 read the Editing an add-on to change its compatibility page from Mozillazine.

Some notes on #2.

  • Download the plugin from the Novell Moonlight download page by right-clicking on the link and selecting Save Link As.
  • After downloading, extract the contents of the .XPI file with an archive manager. The default on Ubuntu should do it.
  • Open install.rdf and look for a line that says <em:targetApplication> <!– firefox –>
  • Below that find the first line that says <em:maxVersion>4.0.*</em:maxVersion>
  • Edit the line accordingly. I am using Firefox 6.0.2. If you are using 5.0.* make the line look like so.

The final version in my case looked like below. Included a few lines to make it more clear:

<em:targetApplication> <!– Firefox –>

What the Mozillazine page does not say is that you have to delete the META-INF folder within the .XPI file so that the install will proceed without a hitch. The META-INF contains MD5 digests and other signatures that will tell Firefox the files have been modified and the install will fail. By deleting this, you are bypassing the safeguards.

Once you have deleted the folder go on and compress the files. A XPI file is only a compressed file using ZIP compression. What you name it doesn’t matter, but do remove the .zip extension after and change it to .xpi. For example, save it as “modified-novell-moonlight-3.99.xpi”.

Install the modified plugin. Select the file from Firefox > File > Open File. You know what to do with the rest. Restart Firefox after.

Now time to test if it works. Find a website that uses Silverlight.

Sample site above is I just Googled for Silverlight sites and this one is among the many in a list.


*Normally you don’t edit the compatibility of a plugin. Is it not safe and it can make your browser unstable and may force it to crash. Do this at your own risk.

** Is Silverlight dead? Has Netflix abandonded Silverlight in favor of HTML5?

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Notice: This article was published on September 24, 2011 and the content above may be out of date.