Free YouTube thumbnail tester: drop in a thumbnail and title to preview them in the home feed, search results, up next sidebar and mobile app, in light and dark mode, with title truncation measured in pixels.
Your thumbnail and title
Thumbnail stays in your browser
No file chosenOr drag an image here, or paste one with Ctrl+V.
0 / 100
How it looks on YouTube
Titles are measured in Roboto and clamped to two lines, using YouTube's desktop layout at a common laptop width and the app on a 390pt phone. Exact widths shift a little with screen size.
How to use this YouTube thumbnail tester
01
Drop in your thumbnail
Choose, drag or paste an image. It is checked against YouTube's size rules and never leaves your browser.
02
Type the title
See it in the home feed, search, the up next sidebar and the mobile app, with the exact point each view cuts it off.
03
Check light and dark
Flip to dark mode, check the sidebar size for readability, and make sure the length badge is not covering anything important.
One thumbnail, four very different sizes
Your thumbnail is designed at 1280 or 3840 pixels wide, but most people see it far smaller: 360 pixels in the desktop home feed, 168 in the up next sidebar. A title that reads fine in search can lose its last words in the sidebar, because every view clamps titles to two lines at a different font size.
This tester draws each placement at its real size and measures the title in Roboto, the font YouTube uses, so the cut happens where it would on the site. It is the same pixel approach behind the SERP simulator, which does this for Google titles and descriptions.
Everything runs in your browser; the image is never uploaded. Posting the video on LinkedIn too? Check the post with the LinkedIn post preview.
Common questions
YouTube's help page recommends 3840 x 2160 pixels for video thumbnails, with a minimum width of 640 pixels and a 16:9 aspect ratio. Use JPG or PNG. From a computer you can upload up to 50 MB; from the YouTube app on a phone the limit is 2 MB. The classic 1280 x 720 still works and clears the minimum easily.
Titles can be up to 100 characters. Every view clamps the title to two lines, so how much shows depends on the space and font size: the up next sidebar shows the least and desktop search shows the most. Because the cut depends on letter widths, this tester measures it in pixels with YouTube's Roboto font instead of guessing a character count.
Many viewers use YouTube's dark theme, where the page around your thumbnail is near black instead of white. Dark thumbnails can melt into the page, and bright ones can look harsh. Toggle the preview to check both before you publish.
In the up next sidebar the thumbnail is only 168 pixels wide, a fraction of its full size. Small text, faces and fine detail disappear first. If your hook is text, make sure it is still readable in the sidebar preview.
Yes. YouTube draws the video length in a dark box in the bottom-right corner of the thumbnail. Keep faces, logos and key text out of that corner. Add your video's length above to see exactly what it covers.
No. The image stays in your browser: it is read locally to draw the previews and never sent to a server or to YouTube. Close the tab and it is gone.