This is crucial. The youtube-mp3-downloader npm package is a tool, and like any tool, its legality depends entirely on your use case.
The package is not a "standalone" solution; it requires external tools to function: youtube-mp3-downloader npm
YD.on("finished", (err, data) => console.log( ✅ Downloaded: $data.file ); ); This is crucial
downloader.on('error', (err) => console.error('❌ Error:', err); ); and like any tool
ffmpeg -version