Test your thumbnail in the real YouTube feed
Home feed, sidebar & search previews · Light and dark mode · Instant 0-100 score · Free, nothing uploaded
What the test covers
Your thumbnail rendered inside the real YouTube home feed, the suggested sidebar at 168px, the mobile app and search results — the exact contexts where it wins or loses the click.
Most YouTube browsing happens in dark mode, where dark thumbnails melt into the background. Every preview switches between light and dark so you catch it before your audience does.
Previews plus eleven deterministic checks — brightness, contrast, text readability, face size — rolled into a 0-100 score, so the test tells you what to change, not just how it looks.
Why testing at full size lies to you
Every thumbnail gets designed on a big, bright editing screen at 1280×720 — and then spends its whole life at a fraction of that size, wedged between competitors, usually on a dark background. That gap is where most "good-looking" thumbnails quietly fail: six words that were crisp in Photoshop become unreadable at sidebar size, and a moody dark frame disappears into dark mode entirely.
A real test reproduces the viewing conditions, not the editing conditions. This tester renders your image inside YouTube's actual surfaces at their actual sizes, flips them between light and dark mode, and then measures what the eye can't judge alone — brightness against the winning range, contrast, text height at 168px, face size. When something misses, the full analyzer report tells you the measured value and the fix.
Already uploaded? YouTube's built-in Test & compare will pick a winner from finished candidates over a couple of weeks. Use this tester to get each candidate right first — and the 9-point checklist for the rules behind every check.
Frequently asked questions
How do I test a YouTube thumbnail before uploading?
Drop the image here (or paste a video link) and you'll see it rendered inside YouTube's real surfaces — home feed, suggested sidebar, mobile, search — in both light and dark mode, alongside a 0-100 score. That's the pre-upload test: does it survive at 168px next to competitors?
How is this different from YouTube's own 'Test & compare'?
YouTube's built-in A/B test is excellent but needs the video published, up to three finished thumbnails, and roughly two weeks of impressions to pick a winner. This tester works before you upload, in seconds, on a single draft — use it to get the design right, then let Test & compare confirm with real viewers.
Why does the sidebar preview matter so much?
Suggested videos render around 168 pixels wide, and it's where a huge share of clicks happen. Text that reads fine in your editor routinely turns to mush there — which is why the tester shows it at that exact size instead of full resolution.
Can I test a thumbnail that's already on YouTube?
Yes — paste the video's link and the tester fetches its thumbnail automatically. Handy for checking how a competitor's design holds up at feed size, or re-testing an old video before you refresh its packaging.
Is my thumbnail uploaded anywhere?
No. The previews and every check run entirely in your browser — the image never leaves your device.