Behind the Scenes of React Native Multithreading: Vision Camera V5 and React Native Worklets
Article Summary
Tomasz J. Żelawski from Software Mansion reveals how React Native finally solved its biggest performance bottleneck. The secret? A multithreading engine that was hiding in plain sight.
For years, React Native developers faced a painful tradeoff: JavaScript's ease of use versus native performance. Heavy tasks like camera processing or animations would bog down the main thread, creating janky experiences. Software Mansion's team extracted their internal worklets solution from Reanimated and turned it into a standalone multithreading library that's now powering VisionCamera v5.
Key Takeaways
- Worklets run JavaScript on separate threads without writing native code
- VisionCamera processes 4K frames (33MB each) without serialization overhead
- Originally built for Reanimated, now extracted as standalone React Native Worklets library
- Enables synchronous frame processing on camera thread at 1GB/s throughput
React Native Worklets brings true multithreading to JavaScript, letting developers run performance-critical code concurrently while staying in familiar territory.
About This Article
React Native developers faced a tradeoff between JavaScript's ease of use and actual performance. Heavy operations like data processing and network calls would run on the shared JS thread, which tanked animation performance.
Software Mansion pulled worklets out of Reanimated and made them into a separate React Native Worklets library. This lets small pieces of JavaScript code run directly on the UI thread with their own JavaScript runtime.
VisionCamera v5 can now process frames synchronously on the camera thread. There's no thread-hopping or serialization overhead anymore, which gets rid of the ~1GB/s data transfer bottleneck that made frame processors impractical before.