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Cannot open pdf files with Firefox's built-in pdf viewer

  • 2 replies
  • 1 has this problem
  • Last reply by Jake-Trapp

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This just started (I think) with Firefox 37.01. This is on Win7-X64. I cannot open pdf files with the Firefox built-in pdf viewer. If I click on the file or try to open it from within Firefox, it brings up a "opening filename.pdf" message. If I select the "Open with" radio button as 'Firefox (default),' it just keeps looping on this process; it never opens. In Tools => Options => Applications, Portable Document Format (PDF) is indicated as 'Preview in Firefox.' I've never had any other PDF viewer installed on this computer. I've tried disabling all plug-ins and extensions, but it still doesn't work. I searched for solutions but haven't found any for this specific issue.

Thanks for the help.

All Replies (2)

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Have you tried, to start Firefox in safemode you can do so by following these steps

If Firefox is open, you can restart in Firefox Safe Mode from the Help menu:

  • Click the menu button New Fx Menu, click Help Help-29 and select Restart with Add-ons Disabled.

If Firefox is not running, you can start Firefox in Safe Mode as follows:

  • On Windows: Hold the Shift key when you open the Firefox desktop or Start menu shortcut.
  • On Mac: Hold the option key while starting Firefox.
  • On Linux: Quit Firefox, go to your Terminal and run firefox -safe-mode
    (you may need to specify the Firefox installation path e.g. /usr/lib/firefox)

When the Firefox Safe Mode window appears, select "Start in Safe Mode".


If the issue is not present in Firefox Safe Mode, your problem is probably caused by an extension, theme, or hardware acceleration. Please follow the steps in the Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems article to find the cause.

To exit Firefox Safe Mode, just close Firefox and wait a few seconds before opening Firefox for normal use again.

When you figure out what's causing your issues, please let us know. It might help others with the same problem.

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Thanks for the suggestion. I had not tried that, but just did, and the problem persists.