i.ytimg.com/vi/iG6YfiTsYOw/maxresdefault.jpg

php - Fetch highest thumbnail resolution - Stack Overflow

All about Thumbnail Images as ytimg maxresdefault

All about Thumbnail Images as ytimg maxresdefault

thumbnail link doesn't work in all cases - Stack Overflow

get-thumbnail option gives url to broken images. · Issue #402

All about Thumbnail Images as ytimg maxresdefault

maxresdefault thumbnail · Issue #373 · nullscreen/yt · GitHub