Publishing a mobile app is not only about code. Apple and Google each expect a consistent set of visual assets—icons at many densities, screenshots at exact pixel dimensions, and (on Apple’s side) strict rules for things like transparency on the App Store icon. This guide walks through what those assets are, why they exist, and how to produce them without spending days in an image editor.
Why platforms demand so many sizes
Phones and tablets have different screen densities. A “point” on iOS maps to 1x, 2x, or 3x pixels; Android uses density buckets (mdpi through xxxhdpi). The same logical icon must look sharp on an older budget phone and a flagship device. That is why you cannot ship a single 64×64 PNG and call it done. Stores also use large marketing-sized images in the listing (Apple’s 1024×1024) that never appear on the Home Screen at full size but must still represent your brand clearly.
iOS: Asset Catalog and App Store Connect
In Xcode, app icons live in Assets.xcassets inside an AppIcon.appiconset. Each slot (20pt notification, 60pt Home Screen, 1024pt App Store, etc.) maps to specific PNG dimensions in Contents.json. If you omit a required slot or use the wrong filename, Xcode warns you; worse, App Store Connect can reject builds or metadata if the marketing icon breaks rules (for example alpha channel on the 1024×1024 asset).
Screenshots are uploaded per device family in App Store Connect. Dimensions change when Apple adds new display sizes. Using a dedicated resizer that tracks the standard iPhone and iPad sizes reduces the risk of uploading a 1242×2208 image when the console now expects a different default for your supported devices.
Android: mipmap and Play Console
Android traditionally uses mipmap (not drawable) for launcher icons so OEMs can pick the best resolution. You provide mdpi through xxxhdpi (and often a round variant). Play Console also asks for a high-res icon and feature graphic; those are separate from the mipmap set inside your APK or App Bundle but should visually match your brand.
Play Store screenshots must meet minimum dimensions on the short edge and fit within allowed ranges for phone vs tablet. Undersized images look soft after upscaling; wrong aspect ratios letterbox. Batch resizing from a single high-quality design export keeps all listing images aligned.
Common mistakes that delay review
- Wrong pixel dimensions—screenshots off by even a few pixels can fail validation or look blurry.
- Transparent App Store icon (iOS)—Apple expects a flat 1024×1024 without alpha for the store listing.
- Unreadable UI at small sizes—logos with tiny text become mud on a real device icon.
- Mixing old and new asset sets—after a platform update, regenerate rather than stretch old PNGs.
Recommended workflow
- Design one master square icon at 1024×1024 or larger in your tool of choice.
- Run it through an app icon generator to produce the full iOS set and Android mipmaps (plus round icons).
- Capture or compose screenshots at the highest resolution you have; frame device chrome in Figma or Sketch if needed.
- Use a screenshot resizer to output every required store size, then upload to App Store Connect and Play Console in one session.
- For non-store sizes (social, blog, email), use custom resize so you do not dilute your store-specific pipeline.
How App Asset Generator fits in
We built this service so the “export forty PNGs” step disappears. You keep creative control in the tools you already use; we handle the mechanical resizing, naming, and ZIP packaging. No account is required, and we do not store your uploads after processing. For questions, see our FAQ and How it works pages.