The ‘Thumbnail Test and Compare’ function will be added to all of YouTube’s channels in the upcoming weeks.
With the help of this functionality, content producers can use three distinct thumbnails for each of their films and see which one works the best.
YouTube will display various thumbnails to viewers at different times during the test. When enough information has been gathered, which might take up to two weeks, YouTube will determine which thumbnail has the most “watch time share.”

YouTube Enables Thumbnail A/B Testing For

Following this analysis, it will assign one of three possible results:
Winner: A thumbnail that performs noticeably better than others in terms of watch time is awarded this title. An algorithm will choose the best thumbnail.

Preferred: Although statistical confidence may be lower, this category suggests that one thumbnail likely outperformed the others.

None: No thumbnail emerges as the clear victor. In this case, the originally uploaded thumbnail will be retained.

For the thumbnail that couldn’t achieve superiority in the test, viewers can manually apply it to their selected video.