Can people read your thumbnail?
Most impressions happen in 168-pixel slots. Box your text and see how tall it really is at every YouTube size, how well it stands off the background, and whether the time badge hides it. Then get three fixes with numbers.
- Text height in px per size
- WCAG contrast
- Time-badge overlap
- Never uploaded
How to use it
- Upload your thumbnail. Drop, choose or paste a 1280x720 thumbnail. It is cropped to 16:9 like YouTube does and never leaves your browser.
- Box the text. Auto-detect marks likely text areas (approximate). Redraw any box that is off, set how many lines each box holds, and box the face if there is one.
- Read the score. See the text height in pixels at each YouTube size, its contrast against the background, clutter, face size and whether the time badge covers it, folded into a 0 to 100 score.
- Apply the three fixes. Each fix names a number to hit, such as a text size or a contrast ratio. Change the design, upload again and compare.
What the score measures
Text size counts most (35 of 100): the tallest text box, measured in the 168-pixel search and sidebar slots. Contrast is next (25), using the weakest box, because one unreadable line is what a viewer notices. Then a clear bottom-right corner (15), a calm background behind the text (15) and a face big enough to read on a phone (10, only when there is a face). A thumbnail with no text boxed is capped at 70, because nothing has proved its text reads.
Want thumbnails that pass at 168px every time?
Shinel Studios designs thumbnails that are checked at feed, search and TV size before you see them.
Frequently asked questions
How big should text be on a YouTube thumbnail?
Big enough to be about 14 pixels tall in the 168-pixel search and sidebar slots, which means the text box should fill roughly a quarter of the thumbnail's height for one line. Three words or fewer is the usual way to get there.
What contrast ratio does thumbnail text need?
Aim for at least 4.5:1 between the text and what is directly behind it, the WCAG level for normal text, and 7:1 if you can. The checker measures it inside each text box by separating the text pixels from the background pixels.
Does the duration badge cover my thumbnail?
Yes. YouTube draws the video length in the bottom-right corner at a fixed pixel size, so it covers a bigger share of the thumbnail in small slots. Keep text and faces out of that corner; the checker shows how much of each text box it hides at every size.
How accurate is auto-detect?
It is an approximate edge and contrast heuristic, not text recognition. It finds dense, high-contrast areas, which are usually text but can be a logo or a busy texture. Redraw any box it gets wrong; the measurements use whatever boxes you leave.
Is my thumbnail uploaded?
No. Everything runs in your browser on a small copy of the image. Nothing is sent to a server or stored, and there is no sign-up.
Why is the TV size measured like a small thumbnail?
On a TV the thumbnail is drawn bigger but watched from the sofa, about two and a half times farther away than a laptop, so text reads roughly like it does in a 170-pixel slot on a desk.
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