For years, React Native performance was constrained by the bridge architecture. Every interaction between JavaScript and the native layer required serializing data into JSON, sending it across an asynchronous pipe, and deserializing it on the other side.
This process introduced latency and traffic jams during heavy user interactions or complex animations. As of 2026, this bridge is effectively legacy technology, replaced by the New Architecture centered on the JavaScript Interface (JSI) and Fabric.
In short
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The legacy bridge architecture relies on asynchronous JSON serialization, which creates performance bottlenecks during high-frequency UI updates.
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The New Architecture replaces this with JSI, allowing JavaScript to hold direct, synchronous references to native C++ objects, eliminating serialization overhead.
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Migrating to the New Architecture is a prerequisite for modern React Native performance, enabling smoother animations and faster startup times by avoiding unnecessary native module initialization.
The Cost of the Bridge
The original bridge acted like a postal service for data. When a user interacted with a component, the system had to package the request, send it, and wait for the native side to process and return a response. This latency was the primary cause of list stutter and animation lag in early React Native applications.
Beyond latency, the old architecture forced the initialization of all native modules at app startup. Whether a user accessed the camera, Bluetooth, or file storage, the system loaded these modules into memory immediately, negatively impacting cold start performance.
JSI and the New Foundation
The JavaScript Interface (JSI) fundamentally changes this by allowing JavaScript to hold a direct reference to native C++ objects. This enables synchronous execution, meaning the JavaScript thread can call native methods directly without waiting for a serialized message to pass through the bridge.
This shift is supported by TurboModules, which JSI to load native modules lazily. Instead of initializing the entire native suite at startup, the app only loads the modules required for the current view. This results in leaner memory usage and significantly faster time-to-interactive metrics.
Architects should prioritize migrating existing codebases to the New Architecture to resolve long-standing performance limitations. While the migration requires updating native modules to be JSI-compatible, the resulting performance gains are essential for maintaining a competitive user experience.
Sources
React Native Bridge vs. JSI: Understanding the New Architecture
https://needlecode.com/blog/mobile-app/react-native-bridge-vs-jsi-new-architecture.html
React Native architecture in 2025: What’s new and what matters
https://globaldev.tech/blog/react-native-architecture
Best Practices for Building AI-Powered Mobile Apps with React Native & Flutter
https://aipxperts.com/blog/best-practices-for-building-ai-powered-mobile-apps-with-react-native-flutter
