WordPress at a glance
action is not described

register_post action-hook . WP 2.1.0

Fires when submitting registration form data, before the user is created.

Usage

add_action( 'register_post', 'action_function_name_9678', 10, 3 );
function action_function_name_9678( $sanitized_user_login, $user_email, $errors ){
	// action...
}
$sanitized_user_login(string)
The submitted username after being sanitized.
$user_email(string)
The submitted email.
$errors(WP_Error)
Contains any errors with submitted username and email, e.g., an empty field, an invalid username or email, or an existing username or email.

Changelog

Since 2.1.0 Introduced.

Where the hook is called

register_new_user()
register_post
wp-includes/user.php 2474
do_action( 'register_post', $sanitized_user_login, $user_email, $errors );

Where the hook is used (in WP core)

Usage not found!