Convert YouTube videos to MP3 or MP4 files and download them for free. 1. Open YouTube.com and go to the video you want to download. Click on the video so that it starts playing. 2. Click on the extension icon in your toolbar and select the download format: MP3 or MP4. 3. A new tab with our website will open, and the conversion will start right away. As soon as it's finished, you can download the file.