HTTP Basic Authentication overview
The Basic Auth module takes a username and password out of the request and authenticates them against Drupal.
It implements the HTTP Basic protocol, in which the username and password are encoded and added to the Authorization header within the request. You can find further details about how it works at its section in Wikipedia.
This module does not offer any user interface. It simply provides an Authentication Provider for Drupal's Authentication Manager to use in order to authenticate a user for a given route.
Here is an example of a route that uses Basic Auth to authenticate users:
# core/modules/system/tests/modules/router_test_directory/router_test.routing.yml module.router_test_11: path: '/router_test/test11' options: _auth: [ 'basic_auth' ] requirements: _user_is_logged_in: 'TRUE' defaults: _content: '\Drupal\router_test\TestContent::test11'
In order to access to
/router_test/test11, you have to fill the Authentication header with a valid Drupal user who has permissions to access to that page.
The REST module supports this method to authenticate requests. There are practical examples of the REST documentation.
Note that Basic Auth is NOT a means of logging into a Drupal site in order to make service GET requests that depend on the identity of the logged-in user (e.g. a views REST display that uses an Authored By relationship to return content belonging to the logged-in user). It is cookie authentication that makes views Relationships possible. See Using other authentication protocols for more on how to login from a client application and get the session cookie.