YouTubeThumbnail Preview

You design a thumbnail big, on your screen, but people meet it small, in a feed full of other videos, often on a phone. Something that looks great full size can turn to mush at 300 pixels wide, or blend in with everything around it.

This preview puts your thumbnail and title among other videos at real sizes, so you can judge it the way a viewer will. The feed is a generic mock-up, and your image stays in your browser.

YouTube recommends custom thumbnails at 1280 × 720 pixels, with a minimum width of 640 pixels, in a 16:9 shape. JPG, PNG and GIF are accepted. Making it at 1280 × 720 keeps it sharp on big screens and TVs, where it's shown much larger.

If your image isn't 16:9, it won't fill the frame cleanly. The image resizer can crop any picture to exactly 1280 × 720.

Look at the preview from arm's length, or squint, and ask:

• Can you tell what it's about at the smallest size, on the phone view?
• Are any words big enough to read? Three or four words is usually the most that works.
• Does the bottom-right corner stay clear? The video length covers it.
• Does it stand out from the cards beside it, in both light and dark mode?
• Do the thumbnail and title work together without repeating each other?

A preview tells you how it looks; only viewers tell you what they click. YouTube Studio's Test & compare lets you upload up to three thumbnails for one video, and YouTube shows them to different viewers and picks the one with the most watch time.

If you don't have that, try changing the thumbnail on an older video that gets steady views, and compare click-through rate over the following week or two.