YouTube Thumbnail Checker

Every weight and cutoff here is our own judgment call, not a figure YouTube publishes, so read the score as a guide rather than a verdict.

Checks based on YouTube's own guidance

Image size, the 16:9 shape it recommends, and the file size limits come from YouTube's thumbnail help page. Text you can read, a design that isn't too complex, and not too much color come from YouTube's thumbnail and title tips. The exact cutoffs we use for those are still ours.

• YouTube Help: Thumbnail & title tips
• YouTube Help: Add custom thumbnails

Legibility Times Pull

The seven niche-weighted metrics blend into two pillars: legibility (brightness, contrast, text, our 120 px phone test: does it read small?) and pull (face, composition, color: does anything grab?). The pillars multiply rather than average, so one strong ingredient can't carry a thumbnail that collapses at the 120px test size. Treat the score as a design health check, not a click prediction.

A missing face or missing text is not marked down: each scores a neutral 70 out of 100. Low color is not marked down either, because YouTube only warns that too much color can overwhelm. If a face or text is there, we score how well it is done. The focal-point heatmap is an estimate from a standard saliency model and is not part of the score. Six caps keep junk low, each holding the score at 40: nothing to read at all (no face, no text, no focal detail with real contrast that survives our 120px test); text too small plus contrast that collapses at the test; an image that is badly under-lit or blown out and also weak at the test; a face or text too small at the test in an image that is also weak at the test; an image under YouTube's 640 pixel minimum; and a file over YouTube's 50 MB limit. When a cap holds the score, the score panel says which one. Our 120px test also checks whether the estimated focal point survives the shrink.

Packaging Reads the Words Off Your Image

Add a title and the checker blends the thumbnail and title scores geometrically, then compares the words on the thumbnail (read by the on-device OCR pass) against the words in the title. Echoing one key term across both halves is free reinforcement; past 25% overlap the pair starts paying for saying the same thing twice, because, by our rule of thumb, the image should add something the title doesn't say. A wordless thumbnail scores neutral here, since it cannot restate anything.

Competitors: Standing Apart

The competitor check measures color, brightness, and saturation gaps against your closest single competitor rather than the group average, because, by our rule of thumb, the risk in a feed is looking like one specific neighbor. Scoring is asymmetric on purpose: being distinguishable earns full marks, and being extra loud past that point earns nothing more. You choose the competitor set, since, by our rule of thumb, the thumbnails you compete with are the ones on your search page.

Client-Side on Purpose

Canvas pixel math plus small on-device face, text, and saliency models. The first analysis takes a few seconds while the models load; after that every run is instant, and your image never leaves your browser. YouTube's help page is checked automatically along the way: at least 640 pixels wide (640 tall for a Shorts thumbnail; 3840x2160 recommended, 2160x3840 for Shorts), under 2 MB if you upload from your phone or 50 MB from a desktop, and the 16:9 shape it recommends (9:16 for Shorts). A different shape, or a file over 2 MB, shows amber. An image under 640 pixels or a file over 50 MB shows red and caps the score at 40. A thumbnail imported from a YouTube link skips the size, shape and file size checks: YouTube already accepted the original, and the copy it serves can be smaller.