YouTube superstar MrBeast rigorously tested his own face across millions of viewers and proved that simply closing his mouth in thumbnails resulted in drastically higher watch…

Why a quieter expression can win a thumbnail test

A thumbnail has a split-second job: persuade someone scrolling past to stop. For years, creators often used wide eyes and open mouths to signal shock or excitement. But an expression that looks dramatic in isolation can become familiar after viewers see it repeated across countless videos. A restrained smile may stand out precisely because it promises interest without shouting for attention.

MrBeast’s reported tests compared versions of his own thumbnails with different facial expressions and found that closed-mouth images performed better on watch time. The useful lesson is not that audiences have permanently rejected excitement. It is that a familiar visual convention can lose its power, and a small change may be worth testing rather than assuming the old formula still works.

What an A/B test can—and can’t—tell you

In an A/B test, different viewers are shown different versions of an image, and the creator compares how people respond. A thumbnail may earn more clicks, but clicks alone do not show whether the video held viewers’ attention. Watch time adds another measure: whether people stayed to watch after choosing the video.

To attribute a result to the expression, the versions need to differ mainly in that feature. If the title, crop, colors, or other details change too, those changes could also affect the outcome. And a result from one creator’s audience is not a rule for every channel; familiarity with the creator and the subject matter can shape what viewers find compelling.

A thumbnail is a promise, not just a reaction

The face helps set expectations before the video begins. An exaggerated gasp promises spectacle; a composed expression can suggest confidence or curiosity. If the image attracts viewers whose expectations match the actual video, the thumbnail has done more than win a click—it has helped bring in an audience willing to stay. That is why testing a subtle expression against a louder one can matter beyond appearance: it tests which promise viewers trust.