Live Activities and Widgets with React: Say Hello to Voltra

Voltra is a new open-source library from Callstack that lets React Native developers build iOS Live Activities and widgets using JSX instead of Swift or SwiftUI. It works by converting JSX into a JSON structure via a custom React renderer, compressing it with Brotli, and passing it to a native SwiftUI renderer. Key features include a hook-based API, remote update support via push notifications (APNs), and several optimizations to fit within iOS's tight 4 KB payload limit — including numeric ID encoding, Brotli compression, and JSX element registry reuse. Image preloading for Live Activities is also handled automatically. Currently in public preview, Voltra is an Expo Module with plans for TurboModule support and eventual Android support.