Mastering Angular Pipes: Types, Examples, and Performance Best Practices

In Angular applications, data often needs to be transformed before being displayed to users. Whether it’s formatting dates, converting text cases, or creating custom transformations, Angular Pipes provide a clean, declarative way to achieve this without cluttering your templates or business logic.

In this blog, we’ll explore:

Why you should use Angular Pipes

Built-in and custom types of Pipes with examples

How Angular Pipes impact performance

Best practices for optimizing Pipes in real-world applications

🔹 What are Angular Pipes?

An Angular Pipe is a feature that allows you to transform data in templates. Pipes are written as simple functions but can be applied in templates using the | (pipe operator).

Example:

<p>{{ user.name | uppercase }}</p>

Here, the uppercase pipe converts the user.name to uppercase before rendering.

✅ Pipes help in separating data transformation logic from the component’s business logic.
✅ They make your templates cleaner and more readable.

🔹 Why Use Angular Pipes?

Declarative Syntax: Instead of writing transformation logic in the component, you apply it directly in the template.

<!-- Without pipe -->
<p>{{ formatDate(user.dob) }}</p>

<!-- With pipe -->
<p>{{ user.dob | date }}</p>

Reusability: A custom pipe can be reused across multiple components without rewriting logic.

Improved Readability: Keeps templates simple and reduces clutter.

Performance Benefits:

Pure pipes are cached and executed only when inputs change.

Helps in reducing unnecessary recalculations.

🔹 Types of Angular Pipes

1. Built-in Pipes

Angular provides several useful built-in pipes out of the box.

📌 Example 1: DatePipe

<p>{{ today | date:'fullDate' }}</p>
<!-- Output: Saturday, September 12, 2025 -->

📌 Example 2: CurrencyPipe

<p>{{ price | currency:'USD':'symbol' }}</p>
<!-- Output: $150.00 -->

📌 Example 3: DecimalPipe

<p>{{ pi | number:'1.2-2' }}</p>
<!-- Output: 3.14 -->

📌 Example 4: PercentPipe

<p>{{ 0.25 | percent }}</p>
<!-- Output: 25% -->

📌 Example 5: SlicePipe

<p>{{ 'AngularPipes' | slice:0:7 }}</p>
<!-- Output: Angular -->

📌 Example 6: AsyncPipe

The async pipe subscribes to an Observable/Promise and automatically handles unsubscribe.

<p>{{ user$ | async }}</p>

1. Custom Pipes

When built-in pipes are not enough, you can create your own.

Example: A pipe to capitalize the first letter of each word

import { Pipe, PipeTransform } from '@angular/core';

@Pipe({
  name: 'capitalize'
})
export class CapitalizePipe implements PipeTransform {
  transform(value: string): string {
    if (!value) return '';
    return value
      .split(' ')
      .map(word => word.charAt(0).toUpperCase() + word.slice(1))
      .join(' ');
  }
}

Usage in template:

<p>{{ 'angular pipes blog' | capitalize }}</p>
<!-- Output: Angular Pipes Blog -->

🔹 Performance and Pipes

While pipes simplify template logic, using them incorrectly can impact performance.

✅ Pure vs Impure Pipes

Pure Pipes (Default)

Executed only when input changes.

Cached results for same input values.

Best for most cases.

Impure Pipes

Executed on every change detection cycle (even if input hasn’t changed).

Useful when working with mutable data (e.g., arrays/objects that change in place).

Can negatively impact performance if overused.

@Pipe({
  name: 'filter',
  pure: false   // Impure pipe
})

✅ Performance Best Practices

Prefer Pure Pipes
Always keep pipes pure unless absolutely necessary.

Avoid Complex Logic in Pipes
Pipes should be lightweight. Move heavy calculations to services or state management.

Leverage AsyncPipe
Instead of manually subscribing/unsubscribing to Observables:

<p>{{ user$ | async }}</p>

Avoid Impure Pipes for Filtering/Sorting Large Lists

Instead of:

<li *ngFor="let item of items | filter:searchText">{{ item }}</li>

Better: Filter data once in the component and bind it.

this.filteredItems = this.items.filter(i => i.includes(this.searchText));

Use TrackBy with NgFor

<li *ngFor="let item of items; trackBy: trackByFn">{{ item }}</li>

🔹 Conclusion

Angular Pipes are a powerful tool for transforming and displaying data in templates. By understanding the difference between built-in and custom pipes, and following performance best practices, you can:

Keep templates clean and maintainable

Achieve better reusability

Ensure optimal performance in large applications

✅ Key Takeaway: Use Angular Pipes for formatting and simple transformations. Keep them pure, lightweight, and leverage async for Observables to unlock maximum performance benefits.

🚀 Rohit Singh 🚀 – Medium

Read writing from 🚀 Rohit Singh 🚀 on Medium. Full-stack developer with 6+ years in Angular, Node.js & AWS. Sharing tips, best practices & real-world lessons from building scalable apps.

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