Are converted mp3 files in stereo?

After conversion from YouTube to mp3, what is the designation of the downloaded file? Mono or stereo?

After conversion from YouTube to mp3, what is the designation of the downloaded file? Mono or stereo?
About 90% of videos uploaded to YouTube are not in stereo.

Videos uploaded to YouTube are generally not of HD quality and stereo on YouTube is guaranteed only with HD video content.
During the conversion of YouTube video content to mp3, the conversion software analyses the video and if it is in stereo, the mp3 file created will also be in stereo, otherwise it will be a simple mono mp3 file (with a single audio channel).

The quality of mono files is still excellent, but the LEFT and RIGHT channels are “merged” into a single one.
Mono files do not, therefore, allow you to appreciate certain stereophonic effects, even with new generation headphones or earbuds.