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What is the difference between AOT and JIT compilation?

Q: What is the difference between AOT and JIT compilation?

**Core concept.** Angular compiles templates to JavaScript. **AOT** (Ahead-of-Time) does this at **build time** — faster startup, smaller bundles, template errors caught during the build, and better security. **JIT** (Just-in-Time) compiles in the **browser at runtime**. Production uses **AOT** (the default); JIT was mainly a development convenience. AOT (build time) fast start, small, secure JIT (in browser) compiles at runtime **How it works.** Tem

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Compare Ahead-of-Time and Just-in-Time.

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AOT is the default build

# Production build → AOT-compiled, optimized, tree-shaken
ng build --configuration production

# Templates compile at BUILD time, so an error like a typo'd binding
#   <p>{{ titel }}</p>     <!-- property 'titel' does not exist -->
# fails the build (AOT) instead of silently breaking at runtime (JIT).

# Since Angular 9 (Ivy), 'ng serve' also uses AOT by default.

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