Free tool · no sign-up · runs in your browser
YouTube Thumbnail Tester
Upload up to three thumbnails, type your title and channel name, and see them side by side and among other videos in a YouTube-style home feed, search results, up-next list and mobile feed, in dark or light mode. Each image is checked against YouTube's thumbnail rules: 16:9, at least 640 px wide, JPG or PNG, and under 2 MB if you upload from the mobile app. Everything runs in your browser; your images are not uploaded.
Upload a thumbnail above to see it here. The cards below are neutral placeholders.
A full week of meal prep in under an hour
Home Kitchen Notes
48K views · 3 days ago
Beginner mistakes I made in my first year of running
Easy Miles
112K views · 1 week ago
Tiny apartment makeover on a small budget
Room by Room
230K views · 2 weeks ago
How to read a topographic map, step by step
Trail Basics
9.4K views · 5 days ago
Testing five cheap desk lamps so you don't have to
Desk Setup Lab
61K views · 4 days ago
Sourdough from scratch: the honest version
Slow Bread
1.2M views · 1 month ago
Approximate layout modeled on YouTube's home feed, search results, up-next list and mobile app. Real sizes change with screen width, and YouTube's design changes over time. Not affiliated with YouTube. The duration badge covers the bottom-right corner, so keep text and faces out of it.
How to use it
- Step 1Upload your thumbnailsAdd one thumbnail, or up to three versions to compare. JPG, PNG, WebP and GIF all preview; each one is checked for size, shape and format.
- Step 2Add the title and channelType the title for each version and your channel name, views, upload age and duration. Add a channel avatar if you like.
- Step 3Compare the layoutsSwitch between side by side, home feed, search results, up next and mobile, in dark or light mode. Shuffle the home feed to see your thumbnail in different positions among other videos.
Turn your thumbnail idea into a short video
Animate the thumbnail image with Kensa's Image to Video, or describe the scene for Text to Video, to make a teaser, a Short or an intro. Video generation uses credits; each clip takes a few minutes.
Frequently asked questions
Is this exactly what YouTube looks like?
No. It is an approximation of YouTube's home feed, search results, up-next list and mobile app, built to judge how a thumbnail and title read at real sizes next to other videos. YouTube's layout changes with screen width and over time, and this tool is not affiliated with YouTube.
What size should a YouTube thumbnail be?
YouTube's help page (checked November 11, 2026) recommends 3840×2160 pixels at a 16:9 aspect ratio, with a minimum width of 640 pixels, as a JPG or PNG. The file limit is 50 MB when you upload from a computer and 2 MB from the mobile app. Custom thumbnails need a verified YouTube account. 1280×720 is still a common size and looks sharp in most places.
Are my images uploaded anywhere?
No. Your thumbnails and avatar are opened directly in your browser and shown from your device's memory. They are not sent to Kensa or anyone else, and they disappear when you close the page.
Can it tell me which thumbnail will get more clicks?
No. It shows how each version looks; it does not predict click-through rate. To measure clicks, use YouTube Studio's thumbnail test where it is available on your channel, or compare results after publishing.
Why does the tool warn about the bottom-right corner?
YouTube places the video length in the bottom-right corner of the thumbnail, so text or a face there gets covered. Turn the duration badge on and off to see what it hides.
Can I test a frame from my video?
Yes. Open the video in the free Video to Thumbnail tool, capture the frame you want and click "Test in Thumbnail Tester". The frame opens here as thumbnail A.
Thumbnail rules from YouTube Help: Add video thumbnails, checked November 11, 2026.