Writing captions for app store screenshots

Most people scroll a store carousel without stopping. The caption is what they read in that half-second, and the screenshot underneath is the evidence. A caption that describes the screenshot is wasted; a caption that states the benefit and lets the screenshot prove it is doing real work.

Benefit above, proof below

"Track every subscription in one place" over a screenshot of a subscription list works. "Subscription list" over the same screenshot does not — the viewer can see that. Write the sentence you would say to a friend who asked why they should install it, then check whether the image below it makes that sentence credible. If it does not, you have the wrong screenshot, not the wrong caption.

Size for the carousel, not for the canvas

Store thumbnails render at a fraction of the exported size. A caption sized to look elegant at full resolution disappears entirely in the carousel. Set the type large enough that it is readable when the image is 300 px wide, which usually means it occupies a meaningful band across the top — far bigger than feels comfortable while you are designing. Three to six words is the working range; anything longer will be skimmed as a shape.

Keep placement and style identical across the set

Captions that move between top and bottom, or change size and colour from image to image, make a set feel like a collage. Fix the position, the type size and the colour once, then only the words change. This also makes localisation dramatically easier: when you translate into eleven languages, a fixed caption band with generous room absorbs longer German and Russian strings without a redesign.