Upgrading from Angular 20 to Angular 21 ensures that your project stays aligned with the latest performance updates, improved developer experience, optimized hydration, and compatibility with new Angular ecosystem tools. This guide walks you through each step clearly so that you can update your application without breaking existing functionality.
1. Why Upgrade to Angular 21?
Angular 21 introduces several improvements across the framework and tooling:
- More optimized Angular compiler for faster builds
- Continued enhancements to Signals & Zone-less apps
- Better SSR + Hydration reliability
- Updated Angular Material components
- Stronger TypeScript support
- Smaller bundles via better tree-shaking
Keeping your app updated ensures long-term stability and better performance.
2. Pre-Upgrade Preparation
Before running upgrade commands, make sure:
✔ You Have the Required Node Version
Check your version:
node -v
Update from nodejs.org if needed.
✔ Backup or Commit Your Project
Never upgrade without Git commits or a full backup.
✔ Update Angular CLI Globally
npm install -g @angular/cli@latest
3. Upgrade Angular 20 → 21 Using CLI
Run the official Angular update command:
ng update @angular/core@21 @angular/cli@21
If your project uses Angular Material:
ng update @angular/material@21
The CLI will automatically:
- Update Angular packages
- Run migrations
- Replace deprecated APIs
- Update TypeScript & RxJS versions if required
4. Additional Updates After Migration
✔ Update TypeScript
Angular 21 may require a newer version:
npm install typescript@latest --save-dev
✔ Update RxJS (If prompted)
ng update rxjs
✔ Update Third-Party Libraries
Ensure compatibility for UI libraries like:
- PrimeNG
- NG-Zorro
- Tailwind plugins
- Form libraries
5. Potential Breaking Changes in Angular 21
Watch for:
- Removal of older deprecated features
- Changes in Material components styling
- Stricter template error checking
- Updated behavior for Signals or listeners
- Zone-less improvements requiring refactoring
- Routing lifecycle changes
Check your terminal logs — Angular CLI alerts you about required fixes.
6. Test Your Application Thoroughly
Run Your Development Server
ng serve
Run Unit Tests
ng test
Build Production Build
ng build --configuration production
If you find issues, search the console or CLI logs for hints.
7. Post-Upgrade Tips
🔹 Reinstall Dependencies (if needed)
rm -rf node_modules
npm install
🔹 Clear Angular Cache
ng cache clean
🔹 Remove Deprecated Syntax
Follow CLI warnings and adjust your code.
8. Final Checks Before Deployment
Before deploying Angular 21 app:
- Test SSR or hydration
- Validate routing flows
- Check Material component UI
- Test forms and APIs
- Commit updated code
You’re now fully upgraded to Angular 21.
Citations
Internal: https://savanka.com/category/savanka-helps/
External: http://angular.dev/