The Mozilla Default Plug-in

By default, Mozilla Firefox comes with the file npnul32.dll in the \Plugins\ directory. If you enter about:plugins in the location bar, you’ll see a list of installed Plug-ins, with file information, and MIME-type assignments. In that list, you’ll see npnul32.dll listed as “Mozilla Default Plug-in”, assigned to the MIME-type *.
So what is the Mozilla Default Plug-in? What does it do? Why is it there? Can one disable it? How does one disable it?

The Mozilla default plug-in is the plugin finder that gets initiated, when you try to load a page that requires a plug-in, which is not found. Whether or not the default plug-in is enabled or disabled dictates how the plugin finder works.
For instance, if don’t have the Macromedia Flash plug-in, then go to their test page, this is what you’ll get with the default plug-in disabled:

This is what you’d get, if the default plug-in is enabled (click on it for full size):

To enable the Mozilla Default plugin, use about:config to change the pref plugin.default_plugin_disabled to false

16 Replies to “The Mozilla Default Plug-in”

  1. I recently updated to Firefox 2.Now, websites are not loading correctly. I can no longer see all images and backgrounds,or colors on web sites.
    I have tried changing settings, updated all plugins-I have tried everything that the Firefox help forums have suggested.I also tried enabling the mozilla default plugin as you described above.Any other ideas? This is driving me crazy!

  2. Karie…I have the exact same problem as you after installing Firefox 2…did you find any solution.


  3. Haha! Downloading plugins automatically is the massive security hole that is the downfall of IE. DO NOT WANT.

  4. You appear to have been hacked. View Source shows there is a hidden iframe with a link to a malicious site at the end of the page. I’ve broken the link here.

  5. “I’ve broken the link here.”
    Apparently the link was stripped from my comment. Just look for the hidden iframe.

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