Keep content off the fold with division regions

When the device is partially folded — held like a book, or propped on a table — the hinge splits the inner display into two usable areas. Content placed across that split is physically bent away from the viewer.

The API

iOS 27.1 introduces ReservedRegion in SwiftUI and UIViewReservedRegion in UIKit. A division region divides a larger area into smaller ones; the hinge is the example that matters here.

GeometryReader { proxy in
    let regions = proxy.reservedRegions(kind: .division)
    let frames = regions.map(\.frame)
    // Lay out so that nothing important intersects `frames`.
}

// UIKit
let regions = view.reservedRegions(kind: .division)
let frames = regions.map(\.frame)

The critical behavioural detail: a division region is active only while the device is folded, and has zero width when the device is flat. Your layout therefore needs to respond to regions appearing and disappearing, not just to their position.

If you want to plan for a region that is not currently active — to avoid a layout jump when the user starts folding — ask for inactive regions too:

GeometryReader { proxy in
    let regions = proxy.reservedRegions(
        kind: .division,
        options: .includeInactive
    )
    let frames = regions.map(\.frame)
}

Prefer arrangements where you can

For the common main-and-secondary case, ArrangementView already consumes active division regions as an input and places your two views on either side of the fold. Query regions directly when you need finer control than an arrangement gives — a custom canvas, a game board, a photo editor.

How to verify

In Device Hub, fold the simulator partway and confirm nothing interactive or load-bearing sits on the division. Then open it flat and confirm the layout closes up cleanly rather than leaving a gap where the hinge used to be.