Most "YouTube thumbnail size" references are upload specs pulled from documentation: max file size, aspect ratio, format. This is the other half — what YouTube's own page actually renders once your image is on it, and where a title actually cuts off. Neither of those is in a spec anywhere; the only way to know them is to load the real page and measure it, which is what this is.
Four surfaces — desktop home grid, desktop search result, the watch-page sidebar, and the
mobile web feed — at three desktop viewport widths (1280 / 1600 / 1920), measured with
getBoundingClientRect and getComputedStyle
in a real, logged-out browser on .
Method, conditions and the raw measurement logs are at
/sources/, so nothing here has to be taken on our word.
Free, CC BY 4.0, no key required. Works from curl, from a server-side fetch, or as a plain download — cross-origin requests from another site's browser JavaScript are not enabled yet, so if you need it client-side, fetch it through your own backend for now. We built this for ourselves and are publishing it because nobody else seems to have it in this form; a link back is appreciated, not required.
https://engagedviews.com/api/surfaces.json
What it doesn't cover: mobile search results and the YouTube phone apps — we couldn't source either, so they're not in here. A dimension is only true as of its measured date, stamped on every entry; YouTube changes layout without notice and we have no fixed schedule for re-checking it.