Video thumbnail

A thumbnail is the still image shown in place of a video before anybody presses play. It appears in email, in search results, in social feeds and on the page itself, and in every one of those places it is doing the work of a headline.

Thumbnails are generated or chosen. A generated thumbnail is a frame taken automatically from the recording, usually near the start, which is why so many videos are represented by a half-blink or an empty desktop. A chosen thumbnail is one the author picked or designed, which almost always performs better because the automatic frame is rarely the most representative one.

For work video the useful rule is that a thumbnail should show either a face or the thing being discussed. A face signals that a person made this for you; an interface signals what the video is about. An empty slide signals neither and is the most common reason a recording goes unwatched.

In email the thumbnail carries an extra constraint: it must be a static image. Mail clients do not reliably animate anything, so a preview that moves in a marketing screenshot is a still frame by the time it reaches an inbox.

It is also the easiest element to test, which is why the teams who care about video test it first. Two thumbnails on the same recording, sent to two halves of a list, will usually separate faster than any other change you could make, because the thumbnail is the only part of the video that everybody sees.