Thumbnail Preview Tester

Compare multiple video thumbnails in realistic PC, tablet, mobile, light, and dark mode previews.

ThumbView Previewer helps creators test YouTube thumbnails before publishing. Upload, paste, or load a thumbnail from a YouTube URL, then preview it inside realistic YouTube-style layouts. See how your thumbnail looks in the home feed, search results, suggested sidebar, mobile feed, and real display sizes. Key features: Preview thumbnails in a YouTube-style feed with real surrounding thumbnail images. Test PC, tablet, and mobile layouts. Switch between light mode and dark mode. Check home feed, search results, suggested sidebar, mobile feed, and size preview views. Upload, drag and drop, paste, or load a public YouTube thumbnail from a video URL. Edit title, channel name, duration, views, and upload age. Shuffle placement to compare your thumbnail against neighboring videos. Use stress tests like squint, monochrome, dim, and tiny view. Review basic thumbnail readiness checks for aspect ratio, resolution, contrast, brightness, and title length. Optionally inject your preview thumbnail into the current YouTube tab for temporary local testing. ThumbView Previewer stores your thumbnail and preview settings locally in Chrome storage. The extension does not require an account and does not collect personal data.