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When using TBB, right-clicking on a link to download it (i.e., "Save Link As...") generally results in the following message:

An external application is needed to handle:

< URL of file to be saved >

NOTE: External applications are NOT Tor safe by default and can unmask you!

I have noticed, though, that this does not happen when I download a plain text file.

Is there some way to download, say, a PDF file without launching an external application?

I've looked at the Applications tab of the Preferences menu hoping I'd find a way to prevent an external application from being invoked, but it was not obvious to me that any changes there would help.

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3 Answers 3

Reset to default
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"Launch application" is a misnomer. This dialog box pops up any time you click on a link to a file that Torbrowser (Firefox) doesn't know how to display on its own, regardless of whether you intend to use an external app or not; unfortunately, it pops up before Firefox gives you the chance to specify what to do with the file in question, and I think this dialog should be reworded to make that clearer. If you click on "Launch" and then select "Save file" in the next dialog, no external app is actually launched - at least, not until you double-click on the saved file. This may be intended as a warning that when you do open the saved file, whatever other program gets used to open that file is out of Tor's control, and could compromise your privacy. Depending on the type of file you're downloading (and your level of paranoia), it may be wise to disconnect from the Internet altogether before opening that downloaded file.

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Downloading the file isn't what this warning is about. You don't need an external application to download the file.

It's about the application you use to open the file. That application isn't configured to use Tor and thus sends information from your actual IP if it opens an internet connection.

If you're sure your PDF viewer doesn't leak information about what you view, you're safe. But I wouldn't be sure about that. PDFs can contain many forms for rich content and I wouldn't be surprised if some of them could trigger network traffic (perhaps DNS queries).

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  • Thank you. How can I download without triggering and external application? Suppose, for example, I click past the warning message and select the save-to-disk option rather than displaying the file. Am I still opening an external app?
    – Kurious
    Dec 5, 2013 at 13:26
  • @Kurious Just downloading the file does not trigger any external application. Opening the file does.
    – CodesInChaos
    Dec 5, 2013 at 14:36
  • Thank you, but it seems that every time I right-click to "Save Link As...", I'm opening an application, despite the fact that I intend at the next menu to select the option to save to disk rather than the one to open the file. How can I download a file without right-clicking to "Save Link As..." in the first place? Or is there a way to prevent "Save Link As..." from opening an application, as it appears to want to do?
    – Kurious
    Dec 6, 2013 at 20:05
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if you use web browser you will always get such warnings, if you use linux and you know link for the file, maybe you can use wget or other methods of downloading. but I don't know if wget or other options show your IP address...

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  • If you use curl in Tails, it goes through Tor.
    – Jobiwan
    Dec 8, 2013 at 15:50

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