Size classes
Size classes describe how much space an app has, so a layout can adapt. iOS has compact and regular size classes for each dimension, and Android has compact, medium and expanded window size classes by width.
Why it matters
Phones rotate, fold and split, and tablets resize windows, so a layout drawn for one device breaks in the next. Designing by class instead of by device keeps one design valid for them.
The classes change with the window, not the device: a phone in a split window can be compact on one axis and regular on the other.
Size classes on iOS and Android
Also called Window size classes, Breakpoints, Adaptive layout. The same idea in each system, with the values Appetite UI gives it.
| Value | iOS | Android | Appetite UI |
|---|---|---|---|
| Name | Horizontal and vertical size classes: compact, regular | Window size classes: compact, medium, expanded | Platform modes ios-md, ios-lg, android |
| Narrow | Compact width | Compact: width under 600 dp | See below |
| Middle | No middle class | Medium: 600 dp up to 840 dp | See below |
| Wide | Regular width | Expanded: 840 dp up to 1200 dp | See below |
In Appetite UI
The Platform collection has the modes ios-md, ios-lg, android and the two iPhone Duo modes, so one switch on a frame changes the numbers that differ. The iPhone Duo screens show a two-pane layout.
Example
A mail app shows one pane in a compact width and a list beside the message in a regular width. On Android the same switch happens at 600 dp for medium and again at 840 dp for expanded.
Common mistakes
- Designing for named devices only. Design for the class.
- Treating portrait and landscape as the only two layouts.
- Hard-coding a breakpoint copied from the web.
- Forgetting height. Landscape phones are compact in height.
Questions
What are the Android window size classes?
Compact is under 600 dp wide, medium is 600 dp up to 840 dp and expanded is 840 dp up to 1200 dp. There are larger classes above that.
What are iOS size classes?
Each dimension, width and height, is either compact or regular. The system sets them from the device, the window and multitasking.
Sources
The pages the facts above rest on, each read October 30, 2026.