React Native 0.76, released in late 2024, enabled the New Architecture by default. If you are maintaining a React Native app built before 2024, you are likely still on the old bridge-based architecture — and Meta has signalled that the old architecture will be deprecated. Migrating to the New Architecture is not optional long-term, but it requires preparation, particularly for apps with native modules or third-party libraries not yet updated to support it.
This guide walks through what actually changed under the hood, which parts of existing codebases tend to break, and how development teams — especially those building consumer apps for the Indian market — should sequence the migration work.
What the Old Architecture Looked Like
The original React Native architecture used an asynchronous bridge to pass JSON-serialised messages between the JavaScript thread and the native (Java/Objective-C) thread. Every interaction that needed native functionality — network calls, UI updates, device sensor access — had to serialize data to JSON, cross the bridge, execute natively, and serialize the result back.
This design made complex animations janky because animation frames could not synchronize with the JS thread. It caused dropped frames during heavy scroll, and made synchronous native calls impossible. Developers who needed tight native integration often had to resort to workarounds — moving logic entirely to native side or using libraries like Reanimated that ran animation worklets outside the JS thread.
The bridge also initialized all native modules eagerly at startup, regardless of whether the app actually used them on the first screen. An app with forty native modules paid the initialization cost for all forty before showing its first UI frame.
The Three Pillars of the New Architecture
The New Architecture replaces the bridge with three interrelated systems:
JSI (JavaScript Interface) is a C++ layer that allows JavaScript to hold direct references to native objects and call native methods synchronously without serialization. No more JSON over a bridge — JS can call C++ functions directly. This opens the door to shared memory between JS and native, and enables the other two systems to work efficiently.
Fabric is the new UI rendering system built on JSI. Fabric moves layout calculations to a shared C++ layer, enabling synchronous layout measurement (critical for things like onLayout events and scroll-linked animations) and supports React Concurrent Mode features. The shadow tree — the internal representation of your component tree used for layout — now lives in C++ rather than in a separate native thread, allowing it to be accessed from both JS and native simultaneously without bridge overhead.
TurboModules replaces the old NativeModules system. Native modules are lazy-loaded only when accessed, which reduces startup time proportionally to the number of modules your app ships. They can be called synchronously or asynchronously via JSI, giving developers precise control over execution semantics rather than being forced into async-only patterns.
Concurrent Mode and React 18 Features Now Available
The New Architecture unlocks React 18's concurrent features in React Native: startTransition, useDeferredValue, Suspense for data fetching, and automatic batching of state updates. These were unavailable in the old architecture because React Native's bridge could not support React's concurrent scheduler.
In practical terms, startTransition lets you keep the UI responsive while running expensive state updates — for example, filtering a large product catalogue — in the background. The transition update is interruptible; if the user taps something else mid-filter, React can abandon the in-progress render and handle the tap immediately. useDeferredValue defers re-rendering of lower-priority UI elements during rapid input, preventing the input field from stuttering while downstream components update.
These patterns are already standard in React web development. The New Architecture brings React Native to parity, which also means React Native developers can now read and apply web-focused React 18 documentation without needing to mentally filter out what "does not apply to native."
What Breaks During Migration
The most common migration blockers teams encounter:
Third-party native modules not updated for New Architecture. Check each native dependency on the React Native Directory (reactnative.directory) for the "New Architecture Compatible" badge. If a critical dependency is not compatible, you must either wait for the maintainer to release an update, fork and patch it yourself, or find an alternative library. For most popular packages (Firebase, Maps, Camera), maintainers have already shipped New Architecture support — the risk is concentrated in smaller or unmaintained packages.
findNodeHandle and UIManager direct usage. Both are deprecated in the New Architecture. Replace with ref callbacks and the measureInWindow method on the ref. This is a straightforward mechanical refactor but can be spread across many files in older codebases.
Synchronous calls to deprecated APIs. Some patterns that worked on the old bridge — accessing native values synchronously using certain hacks — will not work in the same way. The New Architecture requires explicit opt-in to synchronous calls through JSI rather than relying on bridge timing quirks.
Metro bundler configuration. Some custom Metro configs conflict with the New Architecture's Codegen requirements. Specifically, custom module resolvers that intercept native module imports can break Codegen's static analysis. Audit metro.config.js before upgrading.
Codegen — What It Is and Why It Matters
The New Architecture introduces Codegen: a build-time code generation step that creates typed C++ interfaces from TypeScript type definitions. When you define a TurboModule spec in TypeScript, Codegen generates the C++ and Java/Objective-C glue code automatically during the Android Gradle build and iOS pod install.
The key benefit is that type errors which would previously surface as runtime crashes are now caught at build time. If your TypeScript spec says a method returns a string but the native implementation returns an integer, the build fails with a clear error rather than the app crashing in production when that code path executes.
For teams: TypeScript is now effectively required for native module development in the New Architecture. Flow is still supported but TypeScript is where tooling investment is concentrated, and the community documentation examples are TypeScript-first. If your project uses Flow and you have custom native modules, plan a Flow-to-TypeScript migration for those module spec files as part of the upgrade work.
Migration Steps for an Existing App
Step 1: Audit dependencies. Run npx react-native-new-architecture-check or manually check reactnative.directory for every native module you use. Produce a list of compatible, incompatible, and unknown packages. This audit determines your migration timeline more than any other factor.
Step 2: Upgrade to RN 0.76 or later using the React Native Upgrade Helper at upgrade-helper.dev. The diff view shows exactly which files change between versions. Pay attention to the Android build.gradle and iOS Podfile changes — these are where most conflicts occur during upgrades.
Step 3: Enable the New Architecture. In Android, set newArchEnabled=true in gradle.properties. In iOS, set RCT_NEW_ARCH_ENABLED=1 in your Podfile, then run pod install. Do this on a feature branch, not main.
Step 4: Run the build and resolve Codegen type errors. The most common issue at this stage is missing or incorrect TypeScript specs for custom native modules. Codegen will error with messages pointing to the specific spec files that need updating.
Step 5: Test with Fabric renderer active. Pay particular attention to animated components, ScrollView-heavy screens, gesture handlers, and any component that uses ref-based measurements. Scroll through every major screen on a mid-range Android device (Redmi or Realme), not just a flagship emulator.
Step 6: Run your E2E test suite. Detox or Appium tests across all critical user flows — checkout, authentication, navigation — before releasing. The interop layer handles most incompatible modules silently, but E2E tests surface edge cases that unit tests miss.
Interop Layer — Gradual Migration Path
Meta provides an interop layer that allows old-architecture native modules to work within a New Architecture app without immediate rewriting. This means you can enable the New Architecture and still use libraries that have not been fully migrated — they run through the interop layer, which wraps the old bridge protocol and translates calls to the new JSI interface.
Performance will not be fully optimised for those modules running through the interop layer. A camera module going through the interop layer will work, but will not benefit from synchronous layout or reduced serialization overhead. The app functions correctly, but you will not see the full performance gains until the module is natively migrated.
This is the recommended migration path for large apps: enable the New Architecture with the interop layer active, identify which modules are running through it (the Metro dev server logs this), then migrate or replace them one at a time over two to four sprints rather than attempting a big-bang rewrite across the entire native module layer at once.
Performance Improvements You Can Measure
Teams that have completed migration report measurable improvements across several dimensions. Startup time drops 20–40% in apps with many native modules, because TurboModules lazy loading eliminates the old eager initialization of every module at launch. An app that previously loaded 35 native modules at startup now only initializes the modules actually needed for the first screen.
Animation smoothness improves on mid-range Android devices. Fabric's synchronous layout eliminates the frame drops that occurred when animations had to cross the async bridge between JS and native threads. Lists that previously dropped to 45fps during fast scroll now hold 60fps on Redmi Note series hardware.
Memory footprint decreases in complex navigation-heavy apps. Concurrent rendering allows React to defer and discard low-priority renders that are no longer relevant (e.g., a screen the user navigated away from mid-render), freeing memory that would previously have been consumed completing renders nobody ever sees.
On high-end flagship devices — iPhone 15 Pro, Galaxy S24 — the improvement is less perceptible because those devices had enough raw performance to absorb the old architecture's overhead. The biggest observable gains are on mid-range Android: Redmi, Realme, Moto G series. This matters significantly for Indian apps targeting a broad national user base where mid-range Android dominates real-world install distribution.
Should You Migrate Now or Wait?
For new projects: use React Native 0.76 or later with the New Architecture enabled by default. There is no technical or practical reason to start a greenfield project on the old architecture in 2026.
For existing apps, the decision depends on the dependency audit result. If all your critical native dependencies are already New Architecture compatible, migrate now. The process typically takes one to three weeks for a mid-size app with a competent team — one week for the upgrade and build fixes, one week for testing, and a buffer week for issues found in QA.
If you have one or two blocking incompatible dependencies, set a specific target milestone. Allocate roughly one sprint per blocking dependency to replace or patch it, then migrate. A realistic target for most teams in this situation is completion within two to three months.
If you have five or more incompatible critical dependencies, the interop layer becomes your primary tool. Enable the New Architecture now with the interop layer providing compatibility, then work through the dependency list systematically. The interop layer is not a permanent solution — Meta has not committed to maintaining it indefinitely — but it provides a functioning path rather than a forced big-bang migration.
Waiting beyond mid-2026 carries increasing risk. As Meta formally deprecates the old architecture, security patches and bug fixes will be concentrated in the New Architecture codebase. Staying on the old architecture past that point means running code that receives less maintenance attention from Meta's engineering team.
Frequently Asked Questions
Does the New Architecture change anything about React Navigation?
React Navigation 6 and 7 are fully compatible with the New Architecture. The React Navigation team migrated to support Fabric rendering and TurboModules in their v6.x maintenance releases. If you are using React Navigation 5 or earlier: upgrade to v7 before enabling the New Architecture — v5 has known incompatibilities with Fabric. The upgrade from v5 to v7 has breaking API changes (screen components, navigator composition), so budget a separate sprint for the React Navigation upgrade independent of the New Architecture migration.
Is React Native Reanimated compatible with the New Architecture?
Yes — Reanimated 3.x (released in 2023) was specifically rebuilt to support the New Architecture. Reanimated 3 uses the JSI worklet mechanism to run animation code on the UI thread directly, which is actually more powerful in the New Architecture than in the old bridge model. If you are on Reanimated 2.x: upgrade to 3.x as part of your migration — Reanimated 2 may work through the interop layer but will not run animations at full New Architecture performance. Reanimated 3 with Fabric is the combination that enables truly native 120fps animations on ProMotion displays (iPhone 13 Pro and later).
We have a custom native module for Razorpay integration — does it need to be rewritten?
If you are using the official razorpay-pod or razorpay-android SDK wrapped with the standard RN bridge, you have two options. First, use the New Architecture interop layer — the existing module will work without changes while you plan a proper migration. Second, rewrite the native module spec in TypeScript using the TurboModule spec format, then run Codegen to generate the updated glue code. Option two gives better performance and future-proofs the integration. Razorpay's official documentation as of Q1 2026 includes a TurboModule migration guide for the Flutter and React Native SDKs — check their GitHub for the latest RN module spec.