Standalone Components were introduced in Angular v14. It simplifies component management and reduces boilerplate code that comes with NgModules. This is beneficial for new apps, library designing, or modular architecture development using micro-frontends.

Here’s an in-depth explanation on when and why to use Standalone Components over traditional NgModules, along with a complete example.

What Are Standalone Components?

In traditional Angular, every component had to belong to an NgModule. With standalone components, you can create components that are self-contained, and directly usable without declaring them inside a module.

@Component({ standalone: true, selector: 'app-hello', templateUrl: './hello.component.html', imports: [CommonModule] // Import dependencies directly
})
export class HelloComponent {}

When to Use Standalone Components

1. New Angular Projects

If you’re starting a new Angular project, it’s recommended to use standalone components. It simplifies app architecture and removes the mental overhead of managing modules. No need to create modules for every feature; components import their own dependencies.

2. Feature Isolation or Micro Frontends

In micro frontend architecture or when designing a highly modular app, standalone components make it easier to share and reuse features without worrying about module context or imports.

3. Improved Tree-Shaking and Performance

Since standalone components are self-contained, the Angular compiler can better tree-shake unused parts, resulting in smaller bundle sizes.

4. Better Lazy Loading

Standalone components work natively with Angular’s router and make lazy loading easier, without needing to wrap components in modules.

{
  path: 'about',
  loadComponent: () => import('./about/about.component').then(m => m.AboutComponent)
}

5. Simplified Testing

Testing a standalone component is easier because you don’t need to configure TestBed with a module. You can directly import the component and its dependencies.

 When to Stick with NgModules

  • Legacy projects: Migrating everything to standalone might not be worth the effort.
  • Complex libraries: Libraries that expose many components might still benefit from module-based grouping.
  • Third-party dependencies: Some third-party tools expect module-based setup.

Example: Standalone Components over traditional NgModules

Standalone Component Example

hello.component.ts

import { Component } from '@angular/core';
import { CommonModule } from '@angular/common';
@Component({
  selector: 'app-hello',
  standalone: true,
  template: `<h1>Hello, Standalone Component!</h1>`,
  imports: [CommonModule]
})
export class HelloComponent {}

App Routing (app.routes.ts)

import { Routes } from '@angular/router';
export const routes: Routes = [
  {
    path: 'hello',
    loadComponent: () => import('./hello/hello.component').then(m => m.HelloComponent)
  }
];

Traditional Component in Module

hello.component.ts

@Component({
  selector: 'app-hello',
  template: `<h1>Hello from Module!</h1>`
})
export class HelloComponent {}

hello.module.ts

@NgModule({
  declarations: [HelloComponent],
  imports: [CommonModule],
  exports: [HelloComponent]
})
export class HelloModule {}

app.module.ts or feature import

@NgModule({
  imports: [HelloModule]
})
export class AppModule {}

Conclusion

Use standalone components:

  • For new development.
  • When aiming for simplicity and performance.
  • When implementing lazy-loaded features or micro frontends.

Use NgModules:

  • In legacy applications.
  • When managing complex libraries or third-party dependencies.