Inside React Native's New Architecture: Fabric, JSI, and TurboModules

For years, React Native relied on an asynchronous JSON bridge to communicate between the JavaScript thread and the native platform. While this bridge worked well for standard layouts, it introduced a significant bottleneck for high-frequency operations, such as complex animations, gestures, or fast list scrolling, due to serialization and thread queuing. React Native's New Architecture completely removes this bridge, introducing a new paradigm of direct, synchronous native interaction.

At the foundation of this new model is the JavaScript Interface (JSI). Written in C++, JSI allows the JavaScript engine (Hermes) to hold direct references to native C++ host objects. This means JavaScript code can invoke native methods synchronously on the main thread, bypassing serialization entirely. The elimination of the JSON bridge dramatically reduces method invocation latency, allowing for immediate execution of native tasks.

For the UI layer, React Native introduces Fabric, the new rendering engine. Fabric leverages the synchronous capabilities of JSI to execute layout calculations and render trees. In the old architecture, layout changes were calculated in JavaScript, sent across the bridge, and recreated natively. Fabric calculates layout structures directly in C++ and renders native widgets concurrently, ensuring smooth animations and preventing layout jumps during rapid transitions.

Similarly, native modules have been upgraded to TurboModules. Unlike traditional native modules that had to be initialized during app startup (slowing down load times), TurboModules are loaded lazily. A module is only initialized when JavaScript actually requests it. Furthermore, because TurboModules use strongly typed specifications (CodeGen), the boundary between JavaScript and native C++ is validated at build-time, reducing runtime integration bugs.

Adopting the New Architecture allows mobile development teams to achieve performance identical to fully native Swift or Kotlin applications while retaining the rapid developer iteration cycle of React. As the ecosystem matures in 2026, standardizing on Fabric and Hermes is the key to building high-fidelity, high-performance hybrid applications that feel indistinguishable from their native counterparts.