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Javascript Engines

Path: Computer Tech/Development/Web Design/Web Stack/Javascript Engines.mdUpdated: 2/3/2026

JavaScript engines are responsible for parsing, compiling, and executing JavaScript code.

V8 (Google)

  • Used in Chrome, Edge, Node.js, Deno.
  • Highly optimized with JIT (Just-In-Time) compilation.
  • Converts JavaScript to native machine code using:
    • Ignition (interpreter)
    • TurboFan (optimizer)

SpiderMonkey (Mozilla)

  • Used in Firefox.
  • First-ever JavaScript engine.
  • Uses JIT compilation with:
    • Baseline
    • IonMonkey

JavaScriptCore (Nitro) (Apple)

  • Used in Safari, React Native.
  • Developed by Apple.
  • Uses LLVM-based JIT compilation.

Chakra (Microsoft)

  • Used in older versions of Edge.
  • Microsoft has since switched Edge to V8.

Hermes (Meta/Facebook)

  • Used in React Native.
  • Optimized for mobile devices with ahead-of-time compilation.

Each runtime chooses an engine based on its needs, with V8 being the most widely used across browsers and server-side environments.