App Preview (Video) is the short autoplaying video on a store listing that demonstrates the app in motion — a strong conversion lever when it shows real value in the first few seconds.
An app preview is a 15–30 second video (the App Store allows up to three) that autoplays, muted, in the listing. Because it autoplays without sound, the opening seconds and on-screen text do the work — it has to convey the core value before the user scrolls past. Done well, a preview can lift conversion by showing flow and feel that static screenshots can't; done poorly, a slow or confusing intro can underperform the screenshots it sits beside.
Previews aren't mandatory and aren't always a win, so they're worth testing rather than assuming. The strongest ones lead with the single most compelling action the app performs, keep cuts fast, and rely on captions since most views are silent. On the App Store, the preview's poster frame also matters because it's what shows before playback.
Example
A video editor's preview opens on a one-tap transition effect in the first two seconds — the "wow" moment up front — instead of a logo animation that wastes the autoplay window. Lead with the single most compelling action in the first two seconds, and caption it, because most views are silent.