Test your thumbnail before you publish.
Drop in a thumbnail or paste a video link. You get a 0–100 score from eleven measured checks, the fixes that matter most, and previews in the real YouTube feed.
- Price
- Free
- Checks
- 11, measured
- Your image
- Never uploaded
Why creators use it
Feedback you can act on, before the feed sees it.
Every check is a measurement, not a guess — the same image always gets the same score.
A score you can act on
Eleven deterministic checks (brightness, contrast, sharpness, clutter, text amount, face size and more) roll up into one 0-100 score with prioritized fixes.
See it where viewers do
Preview your thumbnail in the YouTube home feed, suggested sidebar, mobile app and search results, in light and dark mode, before you publish.
Private by design
Analysis runs entirely in your browser, including the face and text detection models. Your thumbnail is never uploaded to a server.
How it works
Scored the way the feed shows it.
Most thumbnails are judged at full size on a big editing monitor, but viewers see them at 168 pixels wide, sandwiched between competitors, usually in dark mode. This tool scores your thumbnail the way the feed treats it: it measures brightness, contrast, saturation and sharpness; counts words and checks whether the text stays readable at sidebar size; detects faces and how much of the frame they fill; and flags anything sitting under YouTube's duration badge.
Every check is a deterministic measurement, not an AI guess, so the same image always gets the same score, and every recommendation tells you the measured value and the winning range. When you've made changes, re-upload and watch the score move.
New to thumbnail design? Start with our 9-point YouTube thumbnail checklistfor the exact rules behind each score, and YouTube's own custom thumbnail guidance for upload sizes and formats.
Is this thumbnail analyzer really free?
Yes. There's no account, no credits, and no watermark.
Is my thumbnail uploaded anywhere?
No. Every check, including face detection and text recognition, runs inside your browser. The image never leaves your device.
What does the score mean?
It's a weighted blend of four groups: technical requirements, visual impact, clarity, and subject. 75+ is strong; below 50 means the prioritized recommendations list has critical fixes for you.
What size should a YouTube thumbnail be?
16:9, at least 640 pixels wide, and ideally much larger — YouTube recommends up to 3840×2160, and 1280×720 is a sensible floor that stays sharp everywhere. The file can be up to 2 MB in the YouTube mobile app or 50 MB when you upload from a computer. The analyzer checks all of this automatically.
Why is the first analysis slower?
The first run downloads the in-browser face and text detection models (a one-time step). They're cached afterwards, so repeat analyses finish in a couple of seconds.
Does it work for Shorts or other platforms?
The checks target standard 16:9 YouTube thumbnails. Most visual metrics (brightness, contrast, clutter, text) are still useful for any platform's cover image.
More free tools
Polish the image first.
Fix the thumbnail before you test it: preview it in the feed, cut out the subject, or get it under the mobile app's 2 MB limit.