YouTube Thumbnail Tester
Preview YouTube thumbnails at different sizes. A/B compare two thumbnails for mobile and desktop views.
Quick Answer
Upload one or two thumbnail images (1280×720px recommended) to see how they look at YouTube’s various display sizes. Thumbnails often appear as small as 168×94px in sidebars — if your text and imagery aren’t readable at that size, redesign.
About This Tool
The YouTube Thumbnail Tester lets you preview how your thumbnail will look at the various sizes YouTube displays across desktop and mobile. Thumbnails are the single most important factor in click-through rate after the title. A thumbnail that looks great at full size may be illegible when shrunk to sidebar size, where most impressions actually happen.
Thumbnail Best Practices
Use large, bold text with no more than 3-5 words. Faces with clear emotions drive higher CTR than text-only thumbnails. Use contrasting colors that stand out against YouTube’s white background. Avoid small details that disappear at thumbnail size. The most successful thumbnails communicate the video’s value proposition in under 2 seconds. Test at the smallest display size (168x94px) to ensure readability.
A/B Testing Thumbnails
YouTube offers built-in A/B testing for thumbnails through YouTube Studio. Upload multiple options and YouTube will show each to a portion of your audience, then select the winner based on CTR. Even without the built-in feature, you can manually swap thumbnails and compare CTR over equal time periods. Small thumbnail changes can yield 20-30% differences in click-through rate.