---
name: mobile-platform-conventions
description: Where iOS and Android genuinely differ in expected behaviour, and where a shared design is fine.
when_to_use: You are designing a screen or flow that ships on both iOS and Android.
tags: [mobile, design]
---

# Share the layout, respect the platform where it is muscle memory

Most of a design ports unchanged. A small number of behaviours are so deeply
learned that violating them reads as a bug rather than a style.

## The differences that actually matter

| | iOS | Android |
|---|---|---|
| Back | swipe from left edge; back button top-left | system back gesture/button — **must** work |
| Primary nav | tab bar, bottom | bottom nav bar (or drawer) |
| Destructive confirm | action sheet from bottom | dialog, centred |
| Text input done | "Done" / return key | often the system back dismisses |
| Sharing | share sheet | share intent |

**System back is the one to get right.** On Android, back must always do
something sensible: close the sheet, pop the screen, and at the root, exit.
A screen that traps back is broken in a way users will not report — they will
just leave.

## Safe areas are not optional

Notches, dynamic islands, home indicators and rounded corners all intrude.
Anything within 16pt of an edge needs safe-area insets, not fixed padding. Test
on a device with a notch and one without.

## Touch targets

44pt minimum on iOS, 48dp on Android. This is the most frequently violated rule
in dense interfaces and the most frequently reported as "the app feels
unreliable" rather than as a size problem.

## What NOT to differentiate

Content layout, spacing scale, typography hierarchy, colour and iconography can
and should be shared. Building two visual designs doubles the work and the bugs
for a difference users do not notice, and it is the usual reason a "platform
conventions" pass runs over.

## Test on the smallest supported device

Layouts are usually designed on a large phone and break on a small one, not the
reverse. The smallest supported screen at the largest system font size is the
worst case, and it takes one simulator run to check.