React Native on iPhone Duo

React Native has no fold or hinge API. There is no useDisplayFeatures, no hinge event, nothing that tells JavaScript the device is folded. As of this writing no React Native or Expo release has shipped iPhone Duo support.

The good news is that the two things that break most often — resizing and safe areas — are already solvable with libraries you probably have installed. Work in two tiers.

Tier 1 — works today, no native code

Safe area insets, handled per edge

This is where React Native apps break on iPhone Duo, and it is worth being blunt about why: the safe area is asymmetric here. iOS moves its controls to one side of the display, so left and right insets differ — and which side depends on the pose and on which half of a Split View your app occupies.