Bringing Hermes to iOS in React Native

Callstack just brought Hermes to iOS, and the performance gains are real. After years of Android exclusivity, React Native's lightweight JavaScript engine finally runs on Apple platforms.

Hermes was originally Android-only when Meta released it in 2019. Callstack led the effort to compile and integrate Hermes for iOS and macOS, shipping it in React Native 0.64. This article breaks down the technical work behind making it happen.

Key Takeaways

• Hermes now runs on iOS and macOS after custom compilation work
• Bytecode precompilation reduces app startup time on both platforms
• AOT compilation eliminates JIT overhead for faster execution
• Full technical guide covers compilation and React Native integration

The article links to a deep technical breakdown of how they actually compiled Hermes for Apple's toolchain and integrated it with React Native's architecture.