React Native 0.84: 8 Key Changes You Need to Know

React Native 0.84 has landed, and it's a big one. This release cements Hermes V1 as the default JavaScript engine, ships precompiled iOS binaries, and continues the removal of legacy architecture components. Whether you're building for iOS or Android, these changes affect performance, build times, and maintenance. Here's what you need to know in eight essential points.

1. Hermes V1 Is Now the Default JavaScript Engine

After initial experimental opt-in in version 0.82, Hermes V1 becomes the default JavaScript engine for both iOS and Android. This next evolution of Hermes delivers meaningful improvements to the compiler and VM, resulting in faster execution and lower memory usage. If you've been using Hermes (the default since 0.70), your app automatically benefits—no extra steps needed.

React Native 0.84: 8 Key Changes You Need to Know

2. Automatic Performance Gains Without Configuration

By switching to Hermes V1, your app experiences enhanced execution speed and reduced memory consumption right out of the box. The engine's advanced optimizations handle JavaScript more efficiently, which translates to smoother animations, faster startup, and less strain on device resources. For most developers, this means a free performance upgrade with zero code changes.

3. No Migration Required for Current Hermes Users

If your project already uses Hermes (the default since React Native 0.70), the upgrade to version 0.84 automatically adopts Hermes V1. No configuration changes, no package.json edits, and no migration scripts. You simply update the React Native version in your dependencies, and the new engine is enabled. This seamless transition ensures you can focus on feature development rather than engine tweaks.

4. How to Opt Out of Hermes V1

Although Hermes V1 is the recommended default, you can revert to the legacy Hermes compiler if needed. Use package manager overrides (set hermes-compiler to 0.15.0 in your package.json via overrides, resolutions, or pnpm.overrides). For iOS, set RCT_HERMES_V1_ENABLED=0 and RCT_USE_PREBUILT_RNCORE=0 when running pod install. For Android, add hermesV1Enabled=false to android/gradle.properties and build from source. See the precompiled binaries section for related details.

5. Precompiled iOS Binaries Ship by Default

React Native 0.84 makes precompiled iOS binaries the standard, eliminating the need to compile the React Native core from source during clean builds. The .xcframework binaries are automatically downloaded and used during pod install, drastically cutting build times. To disable this (e.g., if you need to opt out of Hermes V1), pass RCT_USE_PREBUILT_RNCORE=0 when installing pods—but be prepared for longer builds.

6. Legacy Architecture Code Is Being Removed on iOS

Continuing the path set in 0.82, React Native 0.84 accelerates the removal of Legacy Architecture components on iOS. The experimental RCT_REMOVE_LEGACY_ARCH flag—introduced in 0.83—is now enabled by default. Legacy architecture code is compiled out of your iOS builds, reducing both app size and build time. Developers already on the New Architecture should experience no breakages.

7. Legacy Architecture Removal Also Affects Android

Android is not left behind. As outlined in the React Native RFC, legacy architecture classes are being stripped out incrementally in each release. Version 0.84 continues this cleanup, removing outdated components to streamline the Android runtime. While no specific breaking changes were announced for Android in this release, the trend is clear: the old architecture is being phased out completely across both platforms.

8. Node.js 22 Is Now the Minimum Requirement

React Native 0.84 bumps the minimum Node.js version to 22. This ensures access to modern JavaScript features, improved package management, and better performance in build tooling. If your development environment uses an older Node.js version, you'll need to upgrade before installing this release. Check your version with node -v and update via nvm or your package manager.

React Native 0.84 represents a major leap forward in performance and developer experience. With Hermes V1 as default, precompiled iOS binaries, and continued architecture cleanup, the framework is leaner and faster than ever. Upgrade today to take advantage of these improvements—your users will notice the speed, and your CI pipelines will thank you for the reduced build times.

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