How to enable PDF viewer in Firefox 16 [Step-by-Step]

FF PDF viewer

For the longest time we relied on Adobe Reader to preview PDF files on the web, which added unnecessary load to our computers and not really practical. Then Google Chrome brought PDF viewer to the web browser with a built-in feature; since that time Firefox users have been missing out on this great feature.

The good news is that since Firefox 15, PDF viewer support is part of the browser, but it is disabled by default, and for the time being, it’s up to you to turn it on.


1. Update to the latest version of Firefox.

2. In the address bar, type about:config and press Enter. To continue click the I’ll be careful, I promise! button.

3. Next, in the search box type browser.preferences.inContent and press Enter. Once you see the value in the Preference Name list, double-click it to change the value of “false” to “true”.

about:config Firefox

4. Now once again, in the search box type pdfjs.disabled and press Enter. You’ll see that this value is set to “true”, double-click it to set it to “false”.

FF 16 PDF settings

5. There is one last step. From the file menu, click Tools, then Options. Now, navigate through the Applications tab. Search for Portable Document Format (PDF) value and change its setting to Preview in Firefox.

Preview in Firefox

That should do it! To test, go to your favorite search engine, do a search for a PDF file, click it and it should open up with Firefox.

About the author

Mauro Huculak is a Windows How-To Expert who started Pureinfotech in 2010 as an independent online publication. He has also been a Windows Central contributor for nearly a decade. Mauro has over 15 years of experience writing comprehensive guides and creating professional videos about Windows and software, including Android and Linux. Before becoming a technology writer, he was an IT administrator for seven years. In total, Mauro has over 21 years of combined experience in technology. Throughout his career, he achieved different professional certifications from Microsoft (MSCA), Cisco (CCNP), VMware (VCP), and CompTIA (A+ and Network+), and he has been recognized as a Microsoft MVP for many years. You can follow him on X (Twitter), YouTube, LinkedIn and Email him at [email protected].