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React Native 0.84 - Hermes V1 by Default

· 7 min read
Alex Hunt
Alex Hunt
Software Engineer @ Meta
Alan Lee
Alan Lee
Software Engineer @ Meta
Christian Falch
Christian Falch
Software Engineer @ Expo
Gabriel Donadel Dall'Agnol
Gabriel Donadel Dall'Agnol
Software Engineer @ Expo

Today we're excited to release React Native 0.84!

This release makes Hermes V1 the default JavaScript engine, bringing significant performance improvements to all React Native apps. We've also continued removing the Legacy Architecture on both iOS and Android, and are shipping precompiled iOS binaries by default.

Highlights​

Hermes V1 as Default​

Hermes V1 is now the default JavaScript engine for React Native on both iOS and Android, following the initial experimental opt-in in React Native 0.82.

Hermes V1 represents the next evolution of the Hermes engine, with significant improvements to both the compiler and VM that deliver measurably better JavaScript performance.

What This Means for Your App

  • Automatic performance gains: All apps will use Hermes V1 by default, bringing improved execution speed and reduced memory usage.
  • No migration required: If you're already using Hermes (the default since 0.70), you'll automatically get Hermes V1. No configuration changes needed.
Opting out from Hermes V1

Package manager override

Force the installation of the legacy hermes-compiler package in your package.json:

package.json
"overrides": { "hermes-compiler": "0.15.0" }

iOS

When installing CocoaPods dependencies, pass the RCT_HERMES_V1_ENABLED=0 and RCT_USE_PREBUILT_RNCORE=0 environment variables.

Android

Add hermesV1Enabled=false inside the android/gradle.properties file, and configure the application to build React Native from source.

Precompiled Binaries on iOS by Default​

React Native 0.84 now ships precompiled binaries on iOS by default. Previously introduced as an opt-in, precompiled binaries are now enabled out of the box, significantly reducing build times for iOS apps.

This means you no longer need to compile React Native core from source every time you do a clean build. The precompiled .xcframework binaries are automatically downloaded and used during pod install.

info

If you need to build React Native from source (for example, to opt out of Hermes V1), you can disable precompiled binaries by setting RCT_USE_PREBUILT_RNCORE=0 when installing pods.

Legacy Architecture Components Removed​

Building on the work started in 0.82 (which made the New Architecture the only runtime option), React Native 0.84 continues removing Legacy Architecture code from both iOS and Android. As described in the RFC, we're removing several Legacy Architecture classes in each release.

iOS​

In 0.83, we introduced the experimental RCT_REMOVE_LEGACY_ARCH flag to compile out Legacy Architecture code. In 0.84, this is now the default behaviour — Legacy Architecture code is no longer included in your iOS builds, reducing both build time and app size.

No breakages are expected for apps already on the New Architecture — the Interop Layer code required for compatibility remains in place.

Re-enabling Legacy Architecture code on iOS

If you need to re-enable Legacy Architecture code in your iOS builds, you'll need to build from source. Install CocoaPods dependencies with the following flags:

RCT_USE_PREBUILT_RNCORE=0 RCT_REMOVE_LEGACY_ARCH=0 bundle exec pod install

Android​

Removed Legacy Architecture classes

The following classes have been removed in this release:

com.facebook.react.LazyReactPackage
com.facebook.react.bridge.CxxModuleWrapper
com.facebook.react.bridge.CxxModuleWrapperBase
com.facebook.react.bridge.CallbackImpl
com.facebook.react.bridge.NotThreadSafeBridgeIdleDebugListener
com.facebook.react.bridge.OnBatchCompleteListener
com.facebook.react.bridge.ReactCxxErrorHandler
com.facebook.react.bridge.ReactInstanceManagerInspectorTarget
com.facebook.react.modules.debug.DidJSUpdateUiDuringFrameDetector
com.facebook.react.devsupport.BridgeDevSupportManager
com.facebook.react.uimanager.NativeKind
com.facebook.react.uimanager.debug.NotThreadSafeViewHierarchyUpdateDebugListener
com.facebook.react.uimanager.layoutanimation.LayoutAnimationController
com.facebook.react.uimanager.layoutanimation.LayoutAnimationListener

Node.js 22 Minimum​

React Native 0.84 requires Node.js v22.11 or later. This bump improves the availability of modern JavaScript features across the ecosystem of React Native tooling.

Make sure to update your Node.js version before upgrading. We recommend using a Node version manager like nvm or fnm to manage Node versions.

Other Changes​

React 19.2.3​

This release syncs React 19.2.3 into React Native, including the latest fixes and improvements from the React team.

ESLint v9 Flat Config​

React Native's ESLint config now supports ESLint v9 Flat Config, making it easier to adopt the latest ESLint tooling in your project.

Platform Support​

  • Image formats: React Native 0.84 includes support for additional image formats (HEIC and HEIF), making it easier to work with modern camera outputs and image libraries.
  • PlatformColor: Enhanced testing and support for PlatformColor in animated interpolations and output ranges.
  • Keyboard events on Android: Added onKeyDown/onKeyUp support on Android, enabling keyboard event handling for hardware keyboards and TV remotes.

Accessibility​

Text components with onPress or onLongPress handlers now automatically receive accessibilityRole="link" for improved accessibility support, ensuring screen readers properly announce interactive text elements.

On Android, significant work has been done to fix accessibility state issues with recycled views — ensuring that isClickable and OnClickListener states are properly reset when views are recycled, preventing screen readers from announcing incorrect states.

URL API Improvements​

Added missing standard properties to URL (hash, host, pathname, etc.) and methods to URLSearchParams (get, set, delete, etc.), bringing React Native's URL implementation closer to the web standard. Also fixed a URLSearchParams duplicate entry issue.

Other Breaking Changes​

iOS​

  • Fixed a rare EXC_BAD_ACCESS crash in ImageResponseObserverCoordinator by wrapping observers in reference-counted pointers. This changes the object declarations in the RCTImage observer API, which may affect dependent libraries such as react-native-svg.

Android​

  • Removed BridgeDevSupportManager.

C++​

  • JSBigString now implements jsi::Buffer directly. The BigStringBuffer indirection has been removed (deprecated for now). Code directly subclassing or depending on BigStringBuffer may need updating.

JS​

  • The legacy Perf and Network tabs have been removed from the in-app Element Inspector, as these features are now available in React Native DevTools.

Read the full list of breaking changes in the CHANGELOG for 0.84.

Deprecations​

This release ships two deprecations:

  • Networking: The XHRInterceptor and WebSocketInterceptor APIs are deprecated. Developer tools should use the Chrome DevTools Protocol (CDP) Network domain instead.
  • TurboModules: TurboModuleProviderFunctionType is deprecated.

Acknowledgements​

React Native 0.84 contains over 650 commits from 95 contributors. Thank you for all your hard work!

We want to send a special thank you to those who shipped significant contributions in this release:

Upgrade to 0.84​

Please use the React Native Upgrade Helper to view code changes between React Native versions for existing projects, in addition to the Upgrading docs.

To create a new project:

npx @react-native-community/cli@latest init MyProject --version latest

If you use Expo, React Native 0.84 will be available as part of the expo@canary releases. The next SDK, SDK 56, will be shipped with the next stable release of React Native: 0.85.

info

0.84 is now the latest stable version of React Native and 0.81.x moves to unsupported. For more information see React Native's support policy.