Hermes JavaScript Engine for React Native
Article Summary
Facebook just open-sourced Hermes, a JavaScript engine built specifically for React Native on Android. This isn't just another optimization tweak. It's a ground-up rethink of how JS should run on mobile.
At Chain React, Facebook announced Hermes, a lightweight JavaScript engine designed for the constraints of mobile devices. After analyzing performance data, they realized the JS engine itself was the bottleneck for startup performance and app size, especially on mass-market Android devices with limited resources.
Key Takeaways
- Hermes reduces memory usage, download size, and time to interactive (TTI)
- Built specifically for constrained mobile environments with limited memory and slow storage
- Already available for existing React Native apps with simple integration guide
- Targets mass-market Android devices, not just flagship phones
Hermes tackles React Native's biggest mobile performance bottlenecks by replacing the JavaScript engine with one purpose-built for resource-constrained devices.
About This Article
Facebook found that the JavaScript engine was slowing down React Native apps. On mass-market Android devices with limited memory and slow storage, this became a real problem for startup performance and download size.
Facebook created Hermes, a lightweight JavaScript engine built specifically for mobile. Rather than adapt existing engines designed for desktops, they optimized it from scratch for the constraints of mobile devices.
Hermes makes React Native apps faster on resource-limited devices by using less memory, reducing download size, and cutting time to interactive. Apps become usable much quicker.