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Understanding JSI (JavaScript Interface)

React Native 2026: Bridgeless Architecture & JSI

What is JSI?

JSI is a lightweight, general-purpose layer written in C++ that allows the JavaScript engine (like Hermes) to hold references to C++ Host Objects.

Key Benefits:

  • Direct Access: JS can call native methods directly.
  • Synchronous Execution: You can get return values instantly (e.g., const value = NativeModule.getValue()).
  • Zero Serialization: No more JSON overhead.

JSI is the backbone of the New Architecture, enabling the 'Bridgeless' mode.