Como Descargar Youtube En La Laptop

Hello, I'm from Brazil and I would love if I could upload my flac files. I renamed the flac files to mp3 and I could upload them and they are playable on the android app but on the web player they aren't but I don't know if the files are really lossless when I play them on my smartphone because I don't if the used decoder is for mp3 or flac.