How to Upgrade to Angular 20

With the release of Angular 20 comes incredible features, such as a stable Signals API and zoneless change detection. However, upgrading is not as simple as it seems and requires some planning. Here is a step-by-step guide with codes and other common mistakes that ensures an easy upgrade.

Prerequisites

1. Node.js v20: Angular 20 drops support for Node 18. Verify with node -v.
2. TypeScript 5.8: Update via npm install [email protected].
3. Backup Your Project: Use Git to commit changes before proceeding.

Step 1: Update Angular CLI

Update the global CLI to v20:

npm uninstall -g @angular/cli  
npm install -g @angular/cli@20  

Verify with ng version.

Step 2: Upgrade Project Dependencies

Run the Angular update tool:

ng update @angular/core@20 @angular/cli@20  

This updates package.json and applies migrations for:

• Replacing TestBed.get() with TestBed.inject() [6].
• Migrating ngIf, ngFor, and ngSwitch to the new control flow syntax [6].

Example Migration:

<!-- Before -->  
<div *ngIf="user">{{ user.name }}</div>  

<!-- After -->  
@if (user) {  
  <div>{{ user.name }}</div>  
}  

Step 3: Resolve Breaking Changes

Deprecated Structural Directives

Angular 20 deprecates ngIf, ngFor, and ngSwitch. Use the control flow syntax:

@for (item of items; track item.id) {  
  <div>{{ item.name }}</div>  
}  

TestBed.get() Removal

Replace deprecated calls:

// Before  
const service = TestBed.get(UserService);  

// After  
const service = TestBed.inject(UserService);  

Forms API Updates

New methods like markAllAsDirty() are available:

this.userForm.markAllAsDirty();  

Step 4: Enable Experimental Features (Optional)

Zoneless Change Detection

Add to app.config.ts:

import { provideZonelessChangeDetection } from '@angular/core';  

export const appConfig: ApplicationConfig = {  
  providers: [provideZonelessChangeDetection()]  
};  

Note: Manual change detection may be required for third-party libraries [1][5].

Signal-Based Forms (Developer Preview)

Experimental forms API using signals:

const name = signal('');  
const isValid = computed(() => name().length > 2);  

Step 5: Update Browserslist Configuration

Angular 20 targets browsers released in the last 30 months. Update .browserslistrc:

Chrome >= 107  
Firefox >= 104  
Safari >= 16  

Step 6: Test and Optimize

1. Run Tests: Angular 20 deprecates Karma. Migrate to Web Test Runner or Vitest [1][5].
2. Check Bundle Size: Use ng build --stats-json to analyze with webpack-bundle-analyzer.
3. Verify SSR: Test server-side rendering with ng serve --ssr.

Post-Upgrade Checklist

• Update Angular Material/Material UI if used.
• Ensure third-party libraries (e.g., NgRx, RxJS) are compatible.

Enable stricter TypeScript checks in tsconfig.json:

{  
  "compilerOptions": {  
    "strict": true  
  }  
}  

Troubleshooting Common Issues

• "Cannot find module" Errors: Delete node_modules and package-lock.json, then run npm install.
• Zone.js Warnings: Add ngZone: 'noop' to provideZonelessChangeDetection() if using zoneless mode [5].
• Legacy Browser Support: Adjust .browserslistrc if targeting older browsers (may increase bundle size).

Conclusion

Upgrading to Angular 20 unlocks performance gains and modern reactivity patterns. By following these steps, you’ll mitigate breaking changes and leverage features like Signals and zoneless apps. For large teams, consider incremental adoption of experimental APIs to minimize disruption.

Need Help?

• Use ng update --help for CLI options.
• Refer to Angular’s official update guide .