React Native: What is the difference between React Native Hermes and JavaScriptCore?

JavaScriptCore (JSC) — WebKit's JS engine, was default.

Hermes — Meta's JS engine optimized for React Native.

Key differences:

• Hermes compiles JS to bytecode at build time
• Lower memory usage and faster startup
• Smaller APK/IPA sizes
• Better garbage collection for mobile
• JSC still needed for WebViews

Enabling Hermes:

1// android/gradle.properties
2hermesEnabled=true

When to use JSC:

• Need full ES6+ support edge cases
• WebViews requiring JS engine consistency
• Specific debugging tool requirements