As an avid podcast listener I normally collect new mp3 files from RSS feeds in my browser of choice: Firefox (on Windows).
A few years ago Firefox suddenly stopped downloading mp3s when clicked and instead started playing them in an embedded audio player. I almost never want to listen to audio files this way.
Nothing in the basic settings UI seemed to offer any control over this, but googling turned up the following solution:
about:configin the address box
- Find media.directshow.enabled and set it to false
- Find media.windows-media-foundation.enabled and set it to false
This was effective until a recent update (version 44 I think), when some mp3 links began once again autoplaying using the embedded player. Not all mp3 links were affected for some reason, specific response headers being a factor perhaps.
Googling failed to turn up a fix this time, but I noticed that the media.windows-media-foundation.enabled config setting has been replaced with the abbreviated media.wmf.enabled toggle.
It's a shame the upgrade didn't preserve my user setting, but manually changing it to false means all of my mp3s are once again forced to download.
Update December 2019
The problem with these settings is that they also stop HTML5 video from working.
In Firefox 71.0 I have media.play-stand-alone set to false, media.wmf.enabled set to the default true and have deleted media.directshow.enabled.
This seems to allow HTML5 video and force MP3s to download