Desktop card
320 x 180
Check your YouTube thumbnail before it shrinks.
Drop in a thumbnail and preview it at large, mobile, and tiny feed sizes. The checker estimates contrast, detail, aspect ratio, and small-screen visibility so you can catch weak text or muddy composition before publishing.
Mobile feed
180 x 101
Tiny glance
120 x 68
0visibility score
016:9 fit score
0contrast score
0detail score
0visual balance
0 x 0source size
Thumbnail notes
A quick readability check for creator thumbnails.
Most thumbnail problems only become obvious after the image is reduced in a feed. This checker focuses on the practical things that usually break first: low contrast, tiny text, overpacked detail, wrong aspect ratio, and weak subject focus.
Small-size preview
Compare the same thumbnail at 1280px, 320px, 180px, and a tiny glance size before uploading it anywhere.
Local analysis
Contrast, detail, and aspect checks run with browser canvas. The selected image stays in your session.
Creator-friendly notes
Get a short report you can copy into a design checklist, client note, or thumbnail revision task.
Common YouTube thumbnail checks.
A 16:9 canvas, strong foreground subject, and readable text at 120px wide are safer than a detailed design that only works at full size.
1280 x 720 export
16:9 aspect ratio
Large subject silhouette
Few words of text
High contrast edges
Mobile feed preview
Open the thumbnail size guide for a concise checklist you can use before publishing.
FAQ
How do I check if a thumbnail is readable?
Upload it here and inspect the smallest preview first. If the subject, emotion, or text cannot be understood at 120px wide, simplify the design.
Does this upload my thumbnail?
No. The image is loaded into your browser and analyzed locally with canvas. This version does not send the image to a server.
What is a good YouTube thumbnail size?
A common export target is 1280 by 720 pixels with a 16:9 aspect ratio. The tool flags images that drift far from that shape.
Can this predict click-through rate?
No. It only checks visual basics. Topic, title, audience fit, and channel trust still matter for click-through rate.
Can I use it for podcast or video covers?
Yes. It works for any 16:9 preview image where readability at small sizes matters.
Why do my scores change with crop mode?
Crop mode simulates a strict 16:9 frame. Fit mode shows the full image, including letterboxing if the aspect ratio is different.