According to Spotify's own support page, "Spotify uses 3 quality ratings for streaming, all in the Ogg Vorbis format." (https://support.spotify.com/us/using_spotify/system_settings/what-bitrate-does-spotify-use-for-strea...)
Ogg Vorbis is a free audio format that should work by default in Firefox on Ubuntu Linux. However, when I try to use the Spotify Web Player, the songs will not play, and the Firefox console gives the following error message:
The video on this page can’t be played. Your system may not have the required video codecs for: audio/mp4; codecs="mp4a.40.2", audio/mp4; codecs="mp4a.40.2"
This happens because, by default, Ubuntu does not come with any propietary codecs such as AAC (MP4 audio).
Does the web player really use MP4 audio? Does this mean that the desktop and mobile clients also use MP4, or is it just for the web player? Is the support page outdated?