Major Performance Upgrade Now Active on All New Apps
React Native 0.84 has officially gone live, making the next-generation Hermes V1 JavaScript engine the default on both iOS and Android. The update, released today by Meta's React Native team, promises automatic performance gains and significantly reduced memory usage for all apps built with the framework.
“Hermes V1 isn’t just an incremental improvement—it’s a fundamental re-architecture of the engine that delivers measurable performance leaps,” said Sarah Chen, Engineering Lead for React Native at Meta. “Developers upgrading to 0.84 will see faster execution and lower memory footprints without changing a single line of code.”
Automated Gains, No Migration Required
Apps already using Hermes (the default since version 0.70) will seamlessly transition to Hermes V1. No configuration changes are needed. The new engine includes a revamped compiler and virtual machine that together boost JavaScript execution speed and reduce resource consumption.
Early benchmarks show up to 30% faster script parsing and a 20% reduction in peak memory usage compared to the previous Hermes version, according to internal Meta testing. Developers can opt out if needed via package manager overrides or environment variables.
Precompiled Binaries on iOS Now Out of the Box
React Native 0.84 also ships precompiled iOS binaries by default, a feature previously available as an opt-in. This change eliminates the need to compile React Native core from source during each clean build, drastically cutting build times for iOS apps.
“For teams iterating quickly, those saved minutes per build add up to hours saved every week,” noted James Li, a core contributor to the React Native project. The precompiled .xcframework binaries are automatically downloaded and integrated during pod install. Builds can still be reconfigured to compile from source if needed.
Legacy Architecture Code Purged From Builds
Following the removal of legacy runtime options in version 0.82, this release continues the cleanup by stripping out legacy architecture components from both iOS and Android builds. The change reduces app binary size and compile time.
“We’re committed to the New Architecture as the single path forward,” said Chen. “Each release sheds more of the old code, making the framework leaner and more maintainable.” No breakages are expected for apps already on the New Architecture.
Background
React Native’s Hermes engine debuted in 2019 as an open-source JavaScript engine optimized for mobile. Version 0.70 made Hermes the default. The V1 iteration has been in experimental opt-in since version 0.82. Simultaneously, the New Architecture—including Fabric and Turbo Modules—became the only runtime option in 0.82, prompting a gradual removal of legacy code.
These changes align with Meta’s long-term strategy to streamline React Native’s core, reduce maintenance burden, and deliver faster, smaller apps for end users.
What This Means
For existing developers: Upgrading to 0.84 brings immediate performance improvements and faster iOS builds with no extra work. The Hermes V1 default ensures that all apps benefit from the latest JavaScript optimizations.
For new projects: Starting with 0.84 means tapping into a more efficient, modern foundation from day one, with reduced complexity and smaller binary sizes.
For the ecosystem: The removal of legacy code simplifies library compatibility and encourages adoption of the New Architecture. Node.js 22 is now the minimum required version for development.
Full migration details and opt-out instructions are available in the official release notes and upgrade guide.