See your thumbnail before you publish

1280×720 pixels, a 16:9 picture, at least 640 pixels wide. Save it as a JPG or PNG. Under 2 MB it uploads from anywhere; from a computer YouTube takes up to 50 MB, but the phone app doesn’t.

No. Your browser opens it right on your computer and draws the YouTube pages around it, so nothing is sent anywhere. It works for videos you haven’t published yet.

YouTube allows 100 characters, but shows about two lines: on Home and on the phone that’s roughly 50 to 60 characters, and in Up next beside a video even fewer. The tester sets your title at YouTube’s own sizes and tells you where it gets cut, so put the words that make people click first.

Yes. Paste links to videos you compete with, up to five, and they take the place of the made-up videos around yours. Move yours around the feed to see if it still stands out.

Yes. Paste its link instead of dropping in a file, and the tester gets its thumbnail, title and channel. It’s a quick way to see why an old video isn’t getting clicks.

Yes. No account, and no limit on how many thumbnails you test.