5 Game-Changing Updates in React Native 0.84 You Should Know

Introduction

React Native 0.84 has arrived, and it’s packed with improvements that will make your apps faster and your development life easier. This release makes Hermes V1 the default JavaScript engine, ships precompiled iOS binaries out of the box, removes the final pieces of the Legacy Architecture, and bumps the minimum Node.js version to 22. Whether you’re a seasoned React Native developer or just getting started, here are the five most important things you need to know about this update.

1. Hermes V1 Becomes the Default JavaScript Engine

The biggest headline in React Native 0.84 is that Hermes V1 is now the default JavaScript engine on both iOS and Android. First introduced as an experimental opt-in in version 0.82, Hermes V1 represents a major leap forward in performance. It includes a revamped compiler and an improved VM that deliver faster execution speeds and lower memory usage compared to the previous Hermes version. If you’ve been using Hermes (the default since React Native 0.70), your app will automatically benefit from these enhancements—no configuration changes required. For apps that were still on JavaScriptCore, this switch brings immediate performance gains. The upgrade is seamless and happens behind the scenes when you update to 0.84.

2. Automatic Performance Gains Without Any Migration

One of the best parts of this release is that you don’t have to lift a finger to enjoy the performance boost. Since Hermes V1 is the default, all new and existing projects that update to React Native 0.84 will see faster startup times, smoother animations, and reduced memory footprint. The engine is backward-compatible, so your existing code works as-is. If you were already using Hermes, the transition is automatic because the package manager resolves to the new Hermes V1 compiler. This means improved execution speed and lower resource consumption for your end users, all while you focus on building features rather than tweaking build configurations. It’s a win-win situation that makes upgrading to 0.84 a no-brainer.

3. How to Opt Out of Hermes V1 (If Needed)

While Hermes V1 is the default, there are situations where you might need to stick with the legacy Hermes for compatibility reasons. React Native 0.84 provides straightforward opt-out paths for both platforms. For package managers, you can force the installation of the legacy hermes-compiler version (0.15.0) by adding an override in your package.json—for example, using overrides in npm, resolutions in Yarn, or pnpm.overrides. On iOS, set the environment variables RCT_HERMES_V1_ENABLED=0 and RCT_USE_PREBUILT_RNCORE=0 when installing CocoaPods dependencies. On Android, add hermesV1Enabled=false to android/gradle.properties and build React Native from source. These steps ensure you can test or maintain legacy behavior while planning your migration.

4. Precompiled iOS Binaries Speed Up Builds

React Native 0.84 ships precompiled iOS binaries by default, a feature that was previously opt-in. This means that when you run pod install, the React Native core is no longer compiled from source each time—instead, a prebuilt .xcframework is downloaded and linked. The result is significantly faster clean builds and pod installation times. For teams that do frequent clean builds on CI or local machines, this change can shave minutes off your workflow. If you ever need to build from source (for example, if you’re opting out of Hermes V1 or debugging native changes), you can disable this by setting RCT_USE_PREBUILT_RNCORE=0 during pod installation. Otherwise, enjoy the speed boost provided by these precompiled binaries.

5. Legacy Architecture Components Are Fully Removed

Building on the foundation laid in React Native 0.82, which made the New Architecture the only runtime option, version 0.84 continues the cleanup by removing remaining Legacy Architecture code from both iOS and Android. On iOS, the experimental RCT_REMOVE_LEGACY_ARCH flag introduced in 0.83 now defaults to enabled, so legacy classes are compiled out automatically. This reduces both build time and app size. On Android, similar removals have been applied. If your app already uses the New Architecture, you won’t notice any breakage—just a leaner codebase. This removal ensures that future development can focus entirely on the modern architecture, leading to better maintainability and fewer compatibility issues going forward.

Conclusion

React Native 0.84 is a milestone release that delivers tangible benefits: faster JavaScript execution, quicker builds, and a cleaner codebase. With Hermes V1 as the default, precompiled iOS binaries, and the removal of legacy architecture components, upgrading is both simple and rewarding. Remember that Node.js 22 is now the minimum requirement, so make sure your development environment is up to date. If you encounter any issues, the opt-out instructions are clear and easy to follow. Overall, this update solidifies React Native’s position as a modern, high-performance framework for cross-platform mobile development. Upgrade today and experience the difference.