Check a thumbnail against YouTube's current rules — 3840 × 2160 recommended, 16:9, at least 640 px wide, JPG or PNG, up to 50 MB from a computer or 2 MB from the phone app. See it at the small sizes people really see it, and download a copy that fits. Checked in your browser; nothing is uploaded.
Checked entirely in your browser — your image is never uploaded anywhere.
Your thumbnail is checked and resized on this page. It isn't uploaded or saved.
Do this automatically from your episode audio
Thumbnail ready? Spotlight's Episode mode writes the rest from your episode's audio — the description, chapters, title ideas and a post for each platform.
Episode mode is part of the Spotlight workspace on CAPTD's paid plans — see pricing.
Open Episode modeReads the thumbnail's real size and format from the file and checks it against YouTube's help page: 3840 × 2160 recommended, 16:9, at least 640 px wide, JPG or PNG, and the upload limits (50 MB from a computer, 2 MB from the phone app). It shows the thumbnail at small sizes and saves a 16:9 copy under the limit you need.
Every check comes from YouTube's help. A 1280 × 720 thumbnail still uploads — it's just smaller than the 3840 × 2160 YouTube now recommends, so it's marked amber, not red. The small previews are only an illustration of how far a thumbnail shrinks.
YouTube recommends 3840 × 2160 (16:9) for a video thumbnail and 2160 × 3840 for a Short, at least 640 px wide, as a JPG or PNG. Uploads from a computer (and the API) can be up to 50 MB; from the YouTube app on a phone, 2 MB (10 MB for podcasts).
Thumbnails are shown far smaller than that almost everywhere — in search, beside a playing video and on a phone — so a thumbnail that works at full size can be unreadable in the list. YouTube also notes that for vertical videos, a 16:9 thumbnail may be replaced by an automatic 4:5 one in some feeds.
The thumbnail and the title are what people decide on. A file over the limit won't upload, a GIF or WebP isn't accepted, and the wrong shape gets bars or a crop you didn't choose.
YouTube doesn't publish the sizes its pages show thumbnails at, so the small previews are an illustration.