Building Custom HTTP Client Interceptors in Angular

Angular HTTP interceptors allow you to append headers, trace latencies, and catch errors globally. This keeps backend integrations decoupled. If you are looking for complete web builds, look for a senior Full Stack Developer India who specializes in clean frontend-backend contracting.

Defining Functional Interceptors

In Angular 18/21, interceptors are written as simple functions of type `HttpInterceptorFn`. Here is how you append an authorization token:

export const authInterceptor: HttpInterceptorFn = (req, next) => {
  const token = inject(AuthService).getToken();
  const cloned = req.clone({ setHeaders: { Authorization: `Bearer ${token}` } });
  return next(cloned);
};