No, I am not asking how to set a default application or action.
Now that I have that out of the way, I want to know how to determine the default selected radio button for the download dialog:
I would like PDF files to have "Open With" default pre-selected, and everything else to have "Save File" pre-selected. The important thing is that I still want the download dialog to appear, but I don't like how firefox automatically selects one radio button or another (seemingly at random). Someone posted exactly what I am asking for (in much more detail) here: https://support.mozilla.org/en-US/questions/958705#answer-434781
As far as I am aware, Firefox determines what radio button select, but this cannot be changed by the user…
Best Answer
The default actions are determined via the file MimeTypes.rdf, so this file is the one that you should modify once to suite your preferences, then copy to new installations.
Here is an extract from the documentation :
The file should be placed in the Profile folder that is suitable for the operating system and distribution and Firefox version (or fork) that you are using.
The dialog itself will appear with the choices as determined by these settings, or you can set it to automatically execute.
Please note that if you use the same profile on all computers, then Firefox Sync is also a solution.