When I download a file in Firefox, I sometimes get an option to open or save the file, and once set, the default app to use to open the file stays set. But other filetypes only show a save option, even though I've set the filetype in Nemo to open correctly. I can't find any other place to set filetypes other than Firefox and Nemo properties.


If I download an NZB file, the dialog defaults to using SABnzbd, which is desirable. But if I download a .epub file, it only will save the file; I'd like it to open with Calibre ebook organizer, which it did on Ubuntu, my previous OS.


You can use mozplugger to do custom executions based on filetype.

  • Thanks for the tip - I'll look into it, but I'd rather figure out how to do it natively without a plugin. I know it can be done somehow. – Marty Fried Aug 14 '16 at 21:16

Since I was unable to find an answer anywhere on how this is done, I did some experiments, including booting from live USBs of both Cinnamon and Mint. Both did not have the option to open epub files, but did have that option for other unknown or known file types. I tried editing mimeTypes.rdf in the profile directory to remove any type with epub, but that didn't work for me, although the file was not easy to edit, so I can't be sure I did it correctly.

As a last resort, I went back into my old Ubuntu partition, and copied its Firefox profile into the Mint profile, and loaded that profile into Firefox. Lo and behold, I had the expected option to open or download the file.

So, something was added to that profile to enable this option. I see a prefs.js file that might have the option, or perhaps a setting in mimeTypes.rdf, which isn't easy to compare now that I edited the old one.

Since my problem is solved, my priority to figure out the why and how is greatly lowered.

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