thumbnail

A thumbnail is a small representation of a media asset, typically an image or video, used as a preview or navigational cue. It is created by downscaling and possibly cropping the original to a smaller, standard size. Thumbnails help users identify content quickly without loading full-resolution media.

In digital platforms, thumbnails appear alongside galleries, search results, news feeds, and video pages. Video thumbnails often serve as the static poster image for a video and may be a still frame captured from the footage or a custom image designed to attract attention. In file management systems, thumbnail previews show a miniature version of the file's content.

Creation and formats: Thumbnails are generated automatically by servers or software or created manually. Common formats include JPEG, PNG, and WebP; PNG can preserve transparency, JPEG is often used for photographs. Thumbnails are typically scaled to smaller sizes such as 120–320 pixels in width, maintaining aspect ratio.

Technical considerations: Thumbnails should load quickly; techniques include lazy loading and progressive rendering. Descriptive alt text and meaningful filenames aid accessibility and search indexing.

History: The concept originated in pre-digital printing and cataloging where small preview images aided selection; with the rise of digital media, thumbnail generation became automated and integrated into web browsers, file managers, and media platforms.