What is thumbnail?

A thumbnail is the small preview image that represents a video, post or link before someone clicks on it to view the full content.

Thumbnails act like a cover for your content. In crowded feeds and search results, a clear, eye-catching thumbnail can make the difference between someone clicking or scrolling past. This matters especially on YouTube, where thumbnails strongly affect whether people watch.

YouTube lets you upload a custom thumbnail for videos, depending on your account settings. Instagram Reels, TikTok and Facebook let you choose a cover frame or upload a cover image. Link previews use the image set in your web page tags. Each network crops images differently, so check how they look on mobile.

Use bold, simple images with high contrast. Include a face or the product when it makes sense. Add a few large words only if they help. Make sure the thumbnail honestly matches the content, since misleading covers frustrate viewers and hurt trust.

Example

A cooking channel adds a close-up photo of the finished dish and a three-word title to every video thumbnail.