About the thumbnail analyzer
The analyzer measures the pixels in your browser — nothing is uploaded — and shows the thumbnail at four feed sizes, with squint (blurred) and greyscale views that reveal weak contrast and tiny text. It doesn’t pretend to predict click-through rate; it catches the problems that are easy to miss when you’ve been staring at a design up close.
Who it’s for
Creators and designers who want a quick, objective second look at a thumbnail — especially how it holds up small, in dark mode and at a glance.
What makes it different
- Measures the image itself — brightness, contrast, colour and how busy it is — instead of giving a vague score.
- Shows how much of the detail survives at phone size, where most viewers see thumbnails.
- Flags anything important hiding under the duration badge in the bottom-right corner.
- Squint and greyscale previews at four feed sizes. Nothing is uploaded.
How to analyze a YouTube thumbnail
- 1Drop a thumbnail onto the analyzer, choose a file or paste one with Ctrl/⌘+V.
- 2Read the upload checks: resolution, 16:9, file type and the 2 MB app limit.
- 3Read the design checks: brightness, contrast, colour, busyness, phone readability and the badge corner.
- 4Switch to the squint and greyscale views to see the thumbnail the way a scrolling viewer does.
- 5Fix what it flags in the thumbnail maker, then compare versions in the A/B tester.
Features
- Upload checks: resolution, 16:9 ratio, file type and size
- Brightness, contrast and colourfulness measured from the pixels
- Busyness (edge density) and phone readability
- Duration-badge corner check
- Previews at home, search, sidebar and small-phone sizes
- Squint (blur) and greyscale views
- Analyzed in your browser — nothing uploaded
Common use cases
- Final check before upload
- Catch a dark, flat or cluttered thumbnail before it goes live.
- Feedback for a designer
- Give specific notes — “text is lost at phone size”, “badge covers the logo” — instead of “make it pop”.
- Learning thumbnail design
- See why some thumbnails read instantly and others don’t, measured the same way every time.
Tips
- Run the squint view: if you can’t tell what the video is about with the image blurred, simplify it.
- In greyscale the subject should still separate from the background — if not, it’s relying on colour alone.
- Three words or fewer on the thumbnail is usually enough; the title does the rest.
What each check measures
Every check is calculated from the image at feed size, so the numbers reflect what a viewer actually sees rather than the full-resolution file.
- Brightness — the average lightness. Very dark thumbnails fade into dark mode; very bright ones look washed out on the white home feed.
- Contrast — how far light and dark areas are spread apart. Low contrast makes text and faces blur together.
- Colour — how vivid the image is. Muted thumbnails blend in next to other videos.
- Busyness — the share of the image covered by edges. Lots of small elements read as clutter.
- Phone readability — how much of that edge detail is still there at a small phone size. Small text is the first thing to disappear.
- Badge corner — detail in the bottom-right, where YouTube shows the video length.
Related tools
Guides
Thumbnail Analyzer FAQ
Can this predict my click-through rate?
No, and no tool can from the image alone — CTR depends on the title, topic, audience and where the video is shown. The analyzer checks things that make a thumbnail harder to read. To compare real performance, use YouTube Studio’s Test & compare.
What makes a good YouTube thumbnail?
One clear subject, strong contrast, a few large words at most, and nothing important in the bottom-right corner. It should still make sense at phone size and when blurred.
What size should my thumbnail be?
16:9, at least 640 pixels wide; 1280×720 is the common size and YouTube accepts up to 3840×2160. Keep the file under 2 MB if you upload from the YouTube app.
Is my thumbnail uploaded?
No. The image is analyzed in your browser and never leaves your device.