Simplest Method to Enable Firefox Built in PDF Reader Program

Firefox 15 or earlier editions contain PDF reader built into the browser. This function helps to read or view PDF file with Firefox browser. Below listed tips are helpful for those of you wondering how to enable Firefox built in PDF reader, that means you can finally enable or disable the built in PDF reader in Mozilla Firefox.

In my previous post I explored how to set Google Chrome as Default PDF reader and for now I am going to elaborate a suitable method to enable built in PDF viewer Firefox. So if you are searching the same query, then this post will surely help you out. Just follow below instructions:

Enabling Firefox's Built-in PDF Reader

  • Open Firefox and type about:config in the search bar and press enter button.

    enable built in pdf viewer firefox

  • Now second tab will come with a warning message "you might void your warranty". Just click the "I'll be careful, I promise!" button for further process"

    confirm security message

  • Now you can use the search bar to find: browser.preferences.inContent

    search about:config

  • Right click then click the Toggle(you can also press double click to enable or disable the function)

  • In next step, you need to enable the Firefox Built in PDF reader App. For that search: pdfjs.disabled

  • Do right click then press the Toggle option or press double click to enable or disable the function. That's it.

    how to enable firefox built in pdf reader

Now you will be able to view your PDF file with Mozilla Firefox even if the internet connection is not available. Check steps to set Firefox as the default PDF Viewer to always open PDF documents in Firefox Browser.


I have already tried the same method for myself to enable built in PDF viewer on Firefox. So I hope this will also helpful for you to resolve the related queries. Still, feel free to comment if you have any suggestions or doubts about the topic. You can also share your feedback using the comment box.