How To Download/Use YouTube Thumbnail Images
How to download thumbnail images from any video on YouTube, including the auto-generated ones, the low quality ones and the high quality one. Why would you want to download a thumbnail? You might want to use it for a feature image for any theme or web application, for your post or for archive purposes or for any number of reasons.
If you have the URL of the video, you have the video ID. For example, if you have the URL of the video https://youtu.be/nnKFVh8SQ9E or https://www.youtube.com/watch?v=nnKFVh8SQ9E, the video ID is nnKFVh8SQ9E. Now, you can use it in the following URLs:
Small YouTube-generated thumbnail #1 (120x90)
https://img.youtube.com/vi/nnKFVh8SQ9E/1.jpg
Small YouTube-generated thumbnail #2 (120x90)
https://img.youtube.com/vi/nnKFVh8SQ9E/2.jpg
Small YouTube-generated thumbnail #3 (120x90)
https://img.youtube.com/vi/nnKFVh8SQ9E/3.jpg
Small author-selected thumbnail (320x180)
https://img.youtube.com/vi/nnKFVh8SQ9E/mqdefault.jpg
Medium author-selected thumbnail at 4:3 ratio (480x360)
https://img.youtube.com/vi/nnKFVh8SQ9E/0.jpg
Large author-selected thumbnail (1280x720 or 1920x1080)*
https://img.youtube.com/vi/nnKFVh8SQ9E/maxresdefault.jpg
* Only available if video has 720p or 1080p option.