Use pure pipes to improve rendering performance. Pipes are a powerful feature in Angular that allow you to transform data before it is displayed in the view. By default, Angular runs pipes on every change detection cycle, which can be expensive if the data is large or the transformation is complex. Pure pipes, on the other hand, only run when the input data changes, which can significantly improve rendering performance.

To create a pure pipe, you simply need to add the @Pipe decorator with the pure flag set to true. For example, let's say you have a pipe that formats a date:

@Pipe({
  name: 'dateFormat',
  pure: true
})
export class DateFormatPipe implements PipeTransform {
  transform(value: any, format: string): any {
    // format the date
  }
}

In this example, the pure flag is set to true, which tells Angular that the pipe is pure. Angular will then only run the pipe when the input data changes, which can significantly improve performance.