YouTube thumbnail tester
See your thumbnail where it will actually live: squeezed between other videos, at real feed sizes, with the timestamp on top. Add up to three versions to compare, and ask the AI for a blunt review.
I Tried Every Budget Microphone Under $50
Audio Bench · 412K views · 3 days ago
The Easiest Sourdough Method (No Stretch & Fold)
Crumb Club · 1.2M views · 2 weeks ago
Why Nobody Builds Houses Like This Anymore
Structure · 880K views · 1 month ago
Beginner Mistakes in Every Racing Game
Apex Line · 96K views · 5 hours ago
10 Minute Mobility Routine for Desk Workers
Move Daily · 2.1M views · 1 year ago
Upload a thumbnail to see it here. The coloured tiles stand in for competing videos.
What to look for
- Can you read every word in the sidebar view? At about 168 pixels wide, anything under roughly a tenth of the thumbnail height becomes a smudge.
- Does it stand out from its neighbours? If every video in your niche is red and yellow, a blue thumbnail gets noticed.
- Does the timestamp hide anything? Keep faces and words out of the bottom-right corner.
- Does it still work in light mode? Dark thumbnail edges vanish on a dark feed; a thin border or brighter edge helps.
- Is the title doing different work? Read the title and thumbnail together. They should add up to one hook, not say the same thing twice.
Need to fix something? Open the thumbnail maker, or read the legibility guide.
Questions
What does the thumbnail tester show?
Your thumbnail placed among other videos in mock YouTube layouts: the desktop home grid, the mobile feed, the watch-page sidebar and search results, in dark or light mode, at the sizes YouTube uses. It also adds the timestamp chip so you can see what it covers.
Can I compare two thumbnails?
Yes. Add up to three versions and they appear in the same feed, side by side. For a real A/B test with your audience, use YouTube Studio's Test & Compare feature, which splits impressions between up to three thumbnails and picks the one with the most watch time.
Are my images uploaded?
The preview runs entirely in your browser. If you press “Get AI feedback”, a reduced 768×432 copy of that one thumbnail is sent to the AI model for the review and is not stored.
What size is a thumbnail in the YouTube feed?
It varies by screen. On a phone the home feed thumbnail spans the screen width (about 360 to 430 CSS pixels); in the desktop sidebar it is about 168 pixels wide. The size guide has an interactive explainer.