iOS app icon & App Store presence — Icon Composer, screenshots, metadata

Source: Apple HIG App icons, Icon Composer (developer.apple.com/icon-composer), App Store Connect screenshot/preview specs + product-page reference, and App Review Guidelines, plus WWDC26 "Design" guide (developer.apple.com/wwdc26/guides/design) + Platforms State of the Union, cross-checked across ≥2 sources per fact (June 2026). iOS 26 (WWDC25 "Create icons with Icon Composer") is the shipping baseline; iOS 27 (WWDC26) is the current cycle — it refines, not replaces, the Liquid Glass icon system. Apple's through-line: one simple full-bleed mark, no embedded text, no baked corner mask; author Default/Dark/Mono once in Icon Composer; the store page is sold by the first 2–3 screenshots.

1. App icon design fundamentals

• One focal concept. A single, instantly-readable silhouette that expresses the app's purpose. Not a screenshot, not a busy scene, not a UI fragment. If you can't describe it in three words, it's too complex.
• No words / no text. Don't put the app name or taglines in the icon — the name sits under it on the Home Screen and in the store. Lettering is the #1 amateur tell. A single letter-as-logomark is acceptable only if it is the brand mark.
• Full-bleed square, no transparency. Provide a 1024×1024 px square, 90° corners, no alpha channel, art filling the entire canvas. Transparent areas or cutouts get the build rejected.
• Never bake in the rounded mask. iOS applies its own corner radius (a continuous "squircle," not a plain rounded rect) that matches the device. Round it yourself and the system rounds again on top — it reads broken next to real apps. Ship a hard square.
• Legible at small sizes. It renders as small as ~40 pt (notifications, Settings, Spotlight) and in Liquid Glass control sizes. Test at 40px and 29px: fine detail, thin strokes, and gradients with low internal contrast disappear. Favor bold shape + flat or simple color.
• Keyline / proportion. Use Apple's icon grid (in Apple Design Resources / Icon Composer templates) so the mark's optical weight and centering match system apps. Don't let the mark touch the edges unless it's a deliberate full-bleed field.

2. The layered icon system + Icon Composer (iOS 26 baseline → iOS 27)

iOS 26 (Liquid Glass) icons are layered, not one flat PNG. The system relights, blurs, and tints your layers live. Icon Composer (free Apple app, ships with Xcode 26) is the authoring tool; it outputs a single .icon file you drop into Xcode.

Workflow — one master → every variant/size:

• Bring artwork in as layers (foreground / background, up to 4 depth groups); Icon Composer applies Liquid Glass and generates all platform sizes from a single 1024px master (1088px for Watch). No more exporting a size grid by hand.
• Per group you tune Liquid Glass: translucency/opacity, blur, blend mode, specular highlights (crisp edge highlights that define each layer), and neutral or chromatic shadow. A vertical top-down light matches the system UI.
• Drop the .icon into Xcode's navigator; the App Icon field name must match the file name (no extension).