Tip: How to open, unpack or extract *.xpi files

Posted on 19 September 2009

A file with the extension XPI (pronounced zippy) contains a Firefox browser extension. If you are curious about what will be installed if you click on a link containing an XPI resource, you may want to have a look inside.

Extracting XPI

To extract or unpack the XPI, you can rename the file to *.ZIP and open it in your favorite unzip tool. Internally, just like a JAR file, an XPI is basically nothing more than a PKZip compatible archive which you can view and modify using any ZIP utility.

About XPI

XPI contents of np_pdms plugin

XPI contents of np_pdms plugin

An XPI file follows certain guidelines. Once you open it in your favorite unzip program you can see something like in the screenshot (I use WinRAR). And XPI contains the compiled code of a plugin. Understanding the contents of an XPI is rather technical and requires insight knowledge of building plugins for Firefox. Unless you know what you are looking for, it can be hard to find anything useful inside this file.

Some other information on XPI

If your web server also serves XPI files, it must do so with the MIME type application/x-xpinstall.

A valid XPI archive starts with the hexadecimal values 0×50 0x4B 0×03 0×04. A damaged or corrupted file can sometimes be recovered by unzip utilities like WinZip or WinRar. An XPI file contains executable code. Do not install a plugin if you don’t trust the site where you got it from.

– Abel –

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2 responses to Tip: How to open, unpack or extract *.xpi files

  • John laPlante says:

    Thanks for posting this article. I was able to unpack a firefox extension, change the version and rezip it and rename it back and it worked great.

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