Thumbnail swap

The image can be changed at any point, and the video keeps its views, comments and history. Creators do it in two situations: an upload that lands badly in its first day or two, and an older video worth reviving. YouTube's Test and Compare tool does the same job with more discipline, running up to three options across a set period of up to two weeks and picking the winner on watch time rather than on clicks alone. The trap with manual swaps is impatience. Change the image twice in one afternoon and you have destroyed any chance of knowing which version did anything.