YouTube Thumbnail Analyzer: contrast, colours and text at small sizes
Measure contrast, colours, busyness and text size, and compare your thumbnail with up to 4 competitors.
- Free to use
- Runs in your browser
- No sign-up
Add your thumbnail to analyse it
You get its size against YouTube's rules, brightness, contrast, colours, busyness and text readability, side by side with your competitors. Or press Try an example.
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About the YouTube Thumbnail Analyzer
Open your thumbnail and up to 4 competitors' thumbnails, for example screenshots of the videos yours will sit next to. The tool checks your thumbnail's size and shape against YouTube's rules, and measures its brightness, contrast, five main colours, how busy it is, and how readable its text is: the contrast between the words and their background, and how tall they are when the thumbnail is shown small. It shows all of them side by side at feed size, in greyscale and at a small size. Everything runs in your browser; the images are never uploaded.
How it works
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Step 1
Open your thumbnail, then add up to 4 competitors' thumbnails. Press Try an example to see three made-up ones.
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Step 2
Drag on your thumbnail to draw a box round its words, type the box, or press Estimate. The checks update straight away.
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Step 3
Fix what the checks flag, compare the views side by side, and check the final file in the Title and Thumbnail Preview before you upload it.
YouTube's rules and our measures
YouTube recommends thumbnails of 3840 × 2160 pixels in a 16:9 shape, at least 640 pixels wide, as JPG or PNG, up to 2 MB in the mobile app or 50 MB from a computer. Those checks come from YouTube Help. Brightness, contrast, colours, busyness and text size are our own measures: they describe the image, and YouTube does not publish targets for them.
How the measures work
Contrast is the spread between the darkest and lightest 5% of the image. The colours come from a median cut into five groups, and the difference from a competitor is the CIE colour distance between the two palettes. Busyness is the share of pixels on a strong edge. Text contrast uses WCAG's formula, where the accessibility standard asks for 4.5:1 for normal text and 3:1 for large text; text size is measured at 168 pixels wide, as in our preview of the suggested videos list, and our suggestion is at least 12 pixels.
What this tool cannot do
It cannot predict clicks, views or ranking, and it does not detect faces. The text estimate is a guess from strong edges, so mark the box yourself for a better result. Where YouTube shows the video length is our preview, not YouTube's layout. Competitor screenshots are compressed, which can change their colours a little. It does not sign in to YouTube or upload anything.
Frequently asked questions
What size should a YouTube thumbnail be?
YouTube recommends 3840 × 2160 pixels in a 16:9 shape, and accepts thumbnails at least 640 pixels wide. Save it as JPG or PNG: the limit is 50 MB from a computer and 2 MB in the mobile app. Custom thumbnails need a verified account. The analyzer checks these, using the same rules as the Image Size Checker.
Can this tool tell me which thumbnail will get more clicks?
No. The measures describe the image: how bright it is, how much contrast it has, how busy it is and whether its text is readable when small. They do not predict clicks or ranking. To compare thumbnails on real viewers, YouTube Studio's Test & compare can test up to 3 thumbnails on a video and shows the one with the highest watch time.
How is the text contrast worked out?
In the box you mark, the pixels are split into two groups by brightness, and the smaller group is taken as the text. The tool then works out the contrast ratio between the two colours with WCAG's formula. WCAG, the web accessibility standard, asks for at least 4.5:1 for normal text and 3:1 for large text; we use those levels as our measure for thumbnails.
Why does it show my thumbnail so small?
Thumbnails are often seen small, for example in the suggested videos list. The tool measures your smallest line of text at 168 pixels wide, as in our preview, and suggests at least 12 pixels. The small and greyscale views show whether the words and subject still stand out without detail or colour.
Where do I get competitors' thumbnails?
Search YouTube for your topic and take a screenshot of the results, then crop each thumbnail, or save the ones you want to compare. Add up to 4. The tool only reads them in your browser to compare colours, brightness and busyness with yours.
Related reading
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