YouTube thumbnail link doesn't work in all cases

Question

An application I\'m working on needs to get HQ YouTube thumbnails given a URL. Using this answer, I tried using the maxresdefault.jpg to get the maximum resolut

Answer 1

Update 2019 ::

https://i.ytimg.com/vi//hqdefault.jpg

Seems to return highest possible image....

1.jpg, 2.jpg, 3.jpg return previews through the length of the clip which are handy also ;)