What type of authentication is it when a web-browser pops up the logon dialog?

Question

When I go to a website that implements the built-in website logon dialog, what type of authentication is this called?

If I was only talking about IIS, then I would say it is Integrated Windows Authentication, but it can be done with Apache/Linux as well.

It differs from form based authentication (where the page loads and presents the logon dialog from the server) in that it will not let the user read the web page until they authenticate.

Answer 1

I think what you mean is called "Basic Authentication", where the browser gets a 401 HTTP error code when you try to access a protected page. It then displays the dialog box to the user asking to enter the username and password, and sends back the request to the webserver, encoding the username and password in Base64 in one of the header.