To download a YouTube video from a web browser, go to a YouTube downloader website, such as https://y2mate.com or https://savefrom.net. Paste the YouTube link in the search box and tap Start or Download. Choose the video quality and format that you want and tap Download again. To download a YouTube video from an app, download and install a YouTube downloader app, such as TubeMate or VidMate. Open the app and search for the YouTube video that you want to download. Tap on the download icon and choose the video quality and format that you want. Tap Download again.