Difference between AJAX request and a regular browser request

Question

Is there a difference between an AJAX request and a direct browser request (in terms of how a web page is called and loaded)?

In other words, I mean: is a direct ser

Answer 1

Some popular client-side libraries like jQuery include the X-Requested-With header in their requests and set it to XMLHttpRequest to mark them as AJAX.

This seems to have been considered standard enough a few years ago (probably due to the huge popularity of jQuery and its presence in almost every website) that many server-side frameworks even have helpers that take care of checking for this header in the received request for you:

ASP.NET MVC 5:

HttpRequestBase.IsAjaxRequest()

Django:

HttpRequest.is_ajax()

Flask:

flask.Request.is_xhr

However, it seems that with the end of jQuery's reign in the front end world and the standardization of the fetch API and the rise of other modern client-side libraries that don't add any header for this purpose by default, the pattern has fallen into obsolescence also in the backend; with ASP.NET MVC not including the helper in newer versions and Flask marking it as deprecated.