[donmcronald]

I'm pretty skeptical of stuff like that. To me, it looks like they proxy the download for you, but that doesn't make sense because there's no way they have the revenue to support that, right?

How does it work? Can someone explain it to me?

[jeroenhd]

You take youtube-dl/yt-dlp, make a frontend for submitting URLs to it, and stick it in on a page absolutely teeming with ads. With enough ads and enough random people searching for "youtube MP3 downloader" you can cover the server expenses and probably make a few bucks per month in the process.