: Software like ffmpeg is used to strip the video data and re-encode the remaining audio into an MP3 file. Online tools perform this on their own servers before presenting a download link to you, while desktop apps do it locally. Legal Landscape
The legality of these tools depends on the content and how it is used: Youtube To Mp3 Comverter Download
: It downloads the video stream or just the audio track chunks directly from the server. : Software like ffmpeg is used to strip