how to turn youtube into mp3 file code example

Example 1: youtube mp3 converter

You can use WebTools, it's an addon that gather the most useful and basic tools 
such as a synonym dictionary, a dictionary, a translator, a youtube convertor, 
a speedtest and many others (there are ten of them).
You can access them in two clics, without having to open a new tab 
and without having to search for them !

-Chrome Link : 
https://chrome.google.com/webstore/detail/webtools/ejnboneedfadhjddmbckhflmpnlcomge/

Firefox link : https://addons.mozilla.org/fr/firefox/addon/webtools/

Example 2: yt to mp3

Youtube-DL works great. Download from https://youtube-dl.org/. To use, type youtube-dl <url> --audio-format mp3

Example 3: youtube download mp3

I use https://github.com/ytdl-org/youtube-dl/ as a Python CLI tool to download videos