YouTube Thumbnail Preview

A thumbnail that looks great full size on your screen is seen much smaller on YouTube, next to other videos. The preview puts yours in mock versions of the home page, the phone feed, search results and the Up next list, with your title, channel name and length badge, so you see it at the size viewers do.

Your image stays on your device. The tool never uploads it.

Start with Up next, the smallest layout and the toughest test. If you can't tell what the video is about at that size, cut it back to one subject, fewer words and stronger contrast.

Switch between Light and Dark. A thumbnail with a black background can melt into the dark theme, and a pale one into the light theme.

Watch the length badge. It sits in the bottom right corner of the thumbnail, so keep text and faces out of that corner.

Then read the title. YouTube allows up to 100 characters, and the preview warns after 70 because long titles get cut off in feeds and search. It cuts the title to two lines the way YouTube's feeds do, so you can see which words survive.

YouTube recommends custom thumbnails at 3840 x 2160 pixels for videos, in a 16:9 shape, with a minimum width of 640 pixels. JPG and PNG both work. The file limit is 2 MB when you upload from the phone app and 50 MB from a computer. To use a custom thumbnail at all, your YouTube account has to be verified.

When you add an image, the tool shows its pixel size and file size and warns you if it is under 640 pixels wide, not 16:9, over 2 MB or over 50 MB.

A music channel's thumbnail is often a scene and a mood rather than a face. What you are checking is whether the scene still reads at Up next size, and whether the title says what the video is for: study, sleep, rain, focus.

Every Chillframe video comes with a thumbnail made from its own scene, so the picture always matches the video. A Series automatically makes fresh videos on the days you choose and publishes each one to your channel with its title, tags and thumbnail. YouTube accepts custom thumbnails from verified accounts, which is a one-time check.

A 1920 x 1080 image, 1.4 MB

No warnings.

A 1080 x 1080 image

This image is not 16:9, so YouTube will add bars or crop it.

A 1280 x 720 image, 3 MB

Over 2 MB, so upload it from a computer, not the phone app.

Length typed as 225

The badge shows 3:45.