How to Disable/Change Default PDF Viewer in Mozilla Firefox

Mozilla Firefox browser comes with a PDF viewer/PDF plugin by default. Here is a simple tip to disable default PDF viewer in your Firefox.

Method 1

Open up Mozilla Firebox browser and type about:config in the address bar. Select I’ll be careful, I Promise button.

about:config - Mozilla Firefox_007

Type pdfjs.disabled in the search box.

about:config - Mozilla Firefox_009

Right click on pdfjs.disabled and select Toggle.


Now the value will be automatically changed to true.

about:config - Mozilla Firefox_011

Method 2

Open up Firefox. Go to Edit -> Preferences. Select Applications tab.

Firefox Preferences_002

Type pdf in search box.

Firefox Preferences_006

In the Action drop-down box, define the action you want to perform for PDF files. In my case, here I select Use Document Viewer option to view my pdf files.


That’s it. Now your PDF files are automatically opened by your Document viewer instead of opening within Firefox.