Thumbnail Preview Tester
Upload a thumbnail and preview it at every size YouTube actually renders — desktop feed, mobile feed, search results, suggested videos and the small sidebar. The image never leaves your browser.
Your image is read in this browser only. It is never sent anywhere.
· 84K views · 3 days ago
A short description of the video appears here in search results.
Design for the sidebar, not for your monitor
Almost every thumbnail is designed at full size on a large screen and then seen at a fraction of that. The suggested-sidebar preview above is close to the real dimensions a viewer sees, and it is the only one worth judging your design by. If the text is unreadable there, it is unreadable in the place where most of your views actually come from.
What tends to survive at small sizes
One clear subject, high contrast against the background, and three to five words of very large text. What does not survive: thin fonts, long sentences, busy backgrounds, small faces, and anything relying on fine detail. Squint at the sidebar preview — if you cannot tell what the video is about in half a second, neither can anyone scrolling.
Title and thumbnail are one unit
They are always seen together, so they should not say the same thing twice. Let the thumbnail carry the visual hook and the title carry the specifics, or the other way round — but never both. Change the sample title above and watch how differently the same image reads.
Common questions
Is my image uploaded anywhere?
No. The file is read by your own browser and never leaves your device — there is no server involved in this tool at all. Close the tab and it is gone.
Why does my thumbnail look fine large but unreadable small?
Because most viewers never see it large. The sidebar and search previews here are close to real size, and text that survives at that scale is the only text that is doing any work.
What size should a YouTube thumbnail be?
1280 by 720 pixels, 16:9, under 2 MB. But the dimension that matters for design is the smallest one it will be displayed at, not the largest.
How much text should a thumbnail have?
Three to five words is the usual ceiling. If you cannot read it in the sidebar preview on this page, a viewer scrolling past will not read it either.