WordPress Code Reference

SummerySummery

Filters whether a set of user login credentials are valid.

apply_filters( 'authenticate', null|WP_User|WP_Error $user, string $username, string $password )

A WP_User object is returned if the credentials authenticate a user. WP_Error or null otherwise.

$user: (null|WP_User|WP_Error) WP_User if the user is authenticated. WP_Error or null otherwise.
$username: (string) Username or email address.
$password: (string) User password

Changelog
Version	Description
4.5.0	`$username` now accepts an email address.
2.8.0	Introduced.