The required sizes
For iOS you supply one 1024×1024 master icon and modern Xcode generates the rest. The App Store listing icon must be exactly 1024×1024, a flat PNG with no alpha channel. For Android, the Google Play listing needs a 512×512 PNG, plus an adaptive icon built from two 108×108 dp layers. Our free App Icon Size Guide lists every size in one place.
No transparency, no text, no rounded corners
Three rules trip people up most. First, the store icon must be fully opaque — Apple rejects icons with an alpha channel or transparency. Second, do not bake the app name or any words into the icon; it is redundant and looks unprofessional. Third, do not pre-round the corners or add a drop shadow — the platforms apply the rounded mask for you, and doing it yourself produces visible artifacts.
Common rejection and quality issues
Beyond the hard rules, reviewers and users penalize a few recurring problems: icons that are too detailed to read at small sizes, low-resolution or blurry artwork, placeholder or default icons left in by accident, and icons that imply features the app does not have. Trademarked logos or characters you do not own are an instant rejection.
A quick pre-submission checklist: 1024×1024 PNG, no alpha, no text, square (no pre-rounding), high resolution, reads clearly at 40px, and original artwork you have the rights to ship.
Ship clean the first time
The fastest way to stay compliant is to generate your icon with a tool built for the stores. IconGenie outputs a flat, full-bleed, text-free 1024×1024 master plus every platform size and the Xcode/Android assets — so the rules above are satisfied by default and you avoid a rejection round-trip.