*** This article is outdated. The yt-dlp library is a better approach. ***
Read this instead.
1. YoutubeDLD
Add ‘dld’ to the end of youtube. For example:
https://www.youtubedld.com/watch?v=-nuh508dVLo
Default resolution is 720p.
2. YoutubeMY
Add ‘my’ to the end of youtube. For example:
https://www.youtubemy.com/watch?v=-nuh508dVLo
This platform also provides 1080p video but without sound track. To add the sound back, download the MP3 (in fact it is m4a format) separately and use a vido editor to combine the sound and video tracks.
It will start up a player after clicking one of the format buttons. To download the file, click the 3-dot icon at the bottom-right of the player.
Note: As of 2022-01-31, this server has disappeared.
3. VLC Media Player
Copy a URL from a YouTube video, then open up VLC. From the Media menu, select Open Network Stream and paste in the URL. Click Play. When the video is playing, go to Tools > Codec Information. There is a box at the bottom called “Location”—copy the URL you find in that box.
Go back to your browser and paste the URL—it’s a temporary web address and will expire eventually—in the address bar and start playing the video. When you’re viewing the video in the browser, click the 3-dot menu at the lower right for the download option. However, it appears that VLC is only going to save your file as 1080p and not any higher.
If VLC is unable to open the video stream, replace youtube.luac file in the /lua/playlist folder with the latest one downloaded from the offical website, or follow the methods in here: https://www.minitool.com/news/fix-vlc-is-unable-to-open-the-mrl.html
Reference: How to Download YouTube Videos