The new HttpClient was introduced in July 2017 as an improved version of the former Angular HTTP client API, also known as @angular/http, or simply HTTP. Instead of replacing the old version in the @angular/http package, the Angular development team has put the new classes in a separate package--@angular/common/http. They chose to do that to preserve the backward-compatibility with the existing code bases and also to ensure a slow, yet steady migration to the new API.

Those who used the old Angular HTTP service class at least once will most likely remember its main limitations:

• JSON was not enabled by default, forcing the developers to explicitly set it within the request Headers--and JSON.parse/stringify the data--when working with RESTful APIs.
• There was no easy way to access the HTTP request/response pipeline, thus preventing the developer from intercepting or altering the request and/or response calls after they were issued or received, by using some ugly and pattern-breaking hacks. As a matter of fact, extensions and wrapper classes were basically the only way to customize the service, at least on a global scope.
• There was no native strong-typing for request and response objects (although we can cast JSON-as-interfaces as a workaround).

The great news is that the new HttpClient does all of this and much more; other features include testability support and better error handling via APIs entirely based on Observables.