It is quite annoying that Firefox always forgets what application to use for “opening” a file which you just downloaded. Also, the context menu “Open containing folder” in the Downloads overview does not work. Thanks to a hint from user cendryon in  a discussion at LinuxQuestions.org, a clean and simple solution surfaced which I had not thought of myself (even though I implement the same techique in my Dropbox client package):

Using “xdg-open” you can improve the integration of Firefox into your Desktop Environment a lot:

  1. Stop firefox if it is running
  2. Delete or rename the mimetypes cache (where firefox keeps its file association settings):
    $ rm ~/.mozilla/firefox/<yourprofile>/mimeTypes.rdf
  3. Start firefox again
  4. Download any file if you had not done this before
  5. Open that file from the “Tools > Downloads” menu (by right-clicking on it and selecting “Open“). When asked to choose the application for opening the fike, browse to “/usr/bin/xdg-open“. then check the checkbox to “Remember your choice“.

After you’ve configured Firefox like that, both the  “Open” and “Open containing folder” context menus will work. If you are running KDE (which was the subject of that discussion on LQ.org) you can then change the preferred programs through KDE’s “file associations” settings. Brilliant.

Have fun,

Eric