Thumbnail A/B test

YouTube's built-in tool compares up to three thumbnails on a single video and runs for up to two weeks before naming a winner by watch time. Third-party tools do much the same by swapping images on a schedule. Two rules separate a result from noise. Change one thing at a time, so test different thumbnails against the same title or different titles against the same thumbnail. And make the variants obviously different, because audiences do not register a slightly warmer shade of blue and those tests rarely settle on a clear winner.