This site will have limited functionality while we undergo maintenance to improve your experience. If an article doesn't solve your issue and you want to ask a question, we have our support community waiting to help you at @FirefoxSupport on Twitter and/r/firefox on Reddit.

Search Support

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More

Cannot open PDF's in new update

  • 2 cavab
  • 1 has this problem
  • 9 views
  • Last reply by cor-el

more options

Mac OS snow leopard, firefox 36.01...Since the latest update, my pdf downloads try to open as "cgi" files, and then won't open if i say preview.. I checked "extensions" and have none. i looked at my "preferences / applications / file" is already set to "preview"

my current workaround is to use chrome.

Mac OS snow leopard, firefox 36.01...Since the latest update, my pdf downloads try to open as "cgi" files, and then won't open if i say preview.. I checked "extensions" and have none. i looked at my "preferences / applications / file" is already set to "preview" my current workaround is to use chrome.

All Replies (2)

more options
more options

If files get saved with the wrong file extension then you will have to rename them and add the correct file extension, in this case .pdf, yourself to make the file work properly if you double-click the file.

You can try to rename (or delete) the mimeTypes.rdf file in the Firefox profile folder to reset all file actions.


Clear the cache and remove cookies only from websites that cause problems.

"Clear the Cache":

  • Firefox > Preferences > Advanced > Network > Cached Web Content: "Clear Now"

"Remove Cookies" from sites causing problems:

  • Firefox > Preferences > Privacy > "Use custom settings for history" > Cookies: "Show Cookies"