How can I be sure that a browser add-on that is released under the GPL is actually really using the source code that was published?

I read somewhere that the source code of Chrome add-ons is viewable in the Chromium browser directory, is this the same way with Firefox plugins?
I guess not because otherwise there would be no discussion found online regarding the source code of Firefox Add-ons.

1 Answer 1


Firefox add-ons are an XPI file. You have to locate them and then just right click and extract them using tools like 7-Zip.

If you can't locate the addon on your computer then just go to the download page where you can download that particular addon ---> Then right click and select save link as or save target as and save the addon file to your local disk.

After that simply open the .XPI file with any zip extraction software like 7-Zip or WinRAR. The extracted contents might contain the code files.

PS: You can't get source code of every addon by just extracting the addon file. For some add-ons the extracted content may not contain the code files!

If the addon is open source, you should be able to find the source code of addon on respective website.

  • Thanksfor your reply very helpful, i opened one of those xpi files i located them in the .mozilla directory in my home dir. Would the file containing the xource code look like a normal text file with the description source code? Jun 9, 2015 at 21:44
  • It may or may not. It depends upon the developer what naming convention he/she has used. The source code could be a .jar, .js, .css files etc. I have never developed addons by my own so I can't comment much on this part. But I think you shall not find a plain text file as a source code it will be some sort of programming language file.
    – ρss
    Jun 10, 2015 at 9:30

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