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Files and Applications

  • 3 replies
  • 1 has this problem
  • Last reply by jscher2000

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Hello, I am trying to figure out how to prevent the dialog box from prompting me each time I open a pdf attachment. Under applications for PDF I have selected the action to Use Nitro Pro. However, each time I try to open a pdf attachment from my email, I still receive the dialog box; What should Firefox do with the file? Nitro Pro is the default under open with and the "Do this automatically..." is checked. I cannot figure out why the file isn't opening into Nitro without the prompt? Does someone know how to set the options so the pdf opens into the application without being prompted by the dialog box?

Thanks so much, Candie

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It is possible that you created this action with a file type other than the valid "application/pdf" MIME type.
An automatic action will only work properly in that case.
You can possibly check this in handlers.json in the profile folder.

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.


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Hi Candie, you mentioned "attachment" so I assume this is a webmail site like Gmail, Outlook, Yahoo mail, etc.?

Generally speaking, these are well-run sites that probably are avoiding one of the possible rookie mistakes, which is to send Firefox the wrong Content-Type header for the download. It should be "application/pdf" for Firefox to apply your saved action for PDFs.

However, some sites send an additional header which creates a problem, Content-Disposition. When a site sets Content-Disposition to attachment then Firefox is triggered to show you the dialog, even when you do not want to see the dialog.

You can use an add-on to bypass this problem. For example, in mine (, you turn on the extension (click its Zzzz button to wake it up), then click the button again and check the box for "Allow viewing in a tab". If your setting is Save File or Open using Nitro PDF then it won't actually display in a tab, Firefox will follow your saved instructions. I should probably change this item to "Do what I said." Anyway, as long as the extension is running, it will apply that override to all downloads.


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