[[servlet-authentication-authentication]]
= Authentication

The {security-api-url}org/springframework/security/core/Authentication.html[`Authentication`] serves two main purposes within Spring Security:

* An input to <<servlet-authentication-authenticationmanager,`AuthenticationManager`>> to provide the credentials a user has provided to authenticate.
When used in this scenario, `isAuthenticated()` returns `false`.
* Represents the currently authenticated user.
The current `Authentication` can be obtained from the <<servlet-authentication-securitycontext>>.

The `Authentication` contains:

* `principal` - identifies the user.
When authenticating with a username/password this is often an instance of <<servlet-authentication-userdetails,`UserDetails`>>.
* `credentials` - often a password.
In many cases this will be cleared after the user is authenticated to ensure it is not leaked.
* `authorities` - the <<servlet-authentication-granted-authority,``GrantedAuthority``s>> are high level permissions the user is granted.
A few examples are roles or scopes.
