How To Fix Slow Angular Build and Compilation Times?

Angular applications can sometimes experience slow build and compilation times, especially as the project grows larger. Slow builds reduce developer productivity and make testing new features frustrating. This guide explains how to speed up your Angular builds and optimize compilation.

---

1. Understand Why Builds Are Slow

Common reasons for slow Angular builds include:

• Large module and component structures
• Many third-party libraries
• Unoptimized assets and images
• Using JIT (Just-in-Time) compilation in development
• Lack of caching or incremental build setup

---

2. Enable AOT (Ahead-of-Time) Compilation

• Use AOT compilation to precompile templates during build, reducing runtime compilation.

ng build --aot

• This produces optimized output, faster load times, and smaller bundles.

---

3. Enable Differential Loading

• Angular can generate separate bundles for modern and legacy browsers.
• Helps reduce the bundle size and speeds up builds for modern browsers.

ng build --prod

• Differential loading is enabled by default in Angular 10+.

---

4. Optimize Module and Component Structure

• Split large modules into smaller feature modules.
• Use lazy loading to load modules only when required:

{
  path: 'feature',
  loadChildren: () => import('./feature/feature.module').then(m => m.FeatureModule)
}

• Reduces initial bundle size and speeds up incremental builds.

---

5. Minimize Third-Party Libraries

• Only import what’s necessary from libraries.
• Avoid importing entire libraries when only a few components are needed.
• Tree-shake unused modules to reduce build size.

---

6. Use Build Cache and Incremental Compilation

• Angular CLI 14+ supports persistent build cache by default.
• Ensure it is enabled in angular.json:

"cli": {
  "cache": {
    "enabled": true
  }
}

• Speeds up rebuilds by caching unchanged parts of the code.

---

7. Optimize Assets

• Compress images and use modern formats like WebP.
• Serve large assets via CDN instead of bundling them.
• Minimize fonts and heavy CSS libraries that increase compilation size.

---

8. Monitor Performance

• Use Webpack Bundle Analyzer to identify large modules and libraries.
• Profile build times with ng build --stats-json and analyze bottlenecks.
• Continuously review module structure and dependencies to keep build times low.

---

9. Best Practices Summary

• Enable AOT compilation and production mode builds.
• Use lazy loading for large feature modules.
• Keep third-party library imports minimal and tree-shakable.
• Enable Angular CLI caching for faster rebuilds.
• Optimize assets and monitor bundle sizes regularly.

Applying these strategies ensures faster builds, smoother development, and a better developer experience.

---

Citations

Internal: https://savanka.com/category/savanka-helps/
External: http://angular.dev/