Thumbnail Check
Check your YouTube thumbnail at real sizes
See your thumbnail at the sizes YouTube really shows it, and whether the text survives a phone.
Free. Works in any browser, on a phone or a computer. What you put here stays on your device.
About Thumbnail Check
What it checks
- The format: YouTube takes JPG or PNG.
- The file size: up to 50 MB from YouTube Studio on a computer; the YouTube phone app takes 2 MB at most.
- The shape: 16:9 for a video, so nothing is cropped or padded.
- The size: YouTube recommends 3840 × 2160 (4K); narrower than 640 pixels is refused.
- How it reads small: beside other videos in a list, in search and on a phone, with your title next to it.
How to use it
- Drop your thumbnail on the page or choose the file.
- Type the video's title to see how it sits beside the picture and where a list cuts it off.
- Fix what is flagged in your editor, then check again.
What an editor looks for
Most thumbnails are seen at the size of a fingernail. Three words at most, a face or one object big enough to read in the smallest preview, and colours that do not match the title text. If you cannot read it in the smallest preview here, nobody will on a phone.
Rules as read on October 2, 2026 from YouTube Help: Add video thumbnails.
Questions
- Is my picture uploaded anywhere?
- No. The check runs in your browser; the picture never leaves your device.
- Why does the phone app refuse my thumbnail?
- The YouTube phone app takes thumbnails up to 2 MB. Upload it from YouTube Studio on a computer (up to 50 MB), or export a smaller JPG.
- What size should a YouTube thumbnail be?
- YouTube recommends 3840 × 2160 in 16:9. 1280 × 720 still works and looks sharp on most screens.