The following WordPress filter will redirect the wp-login.php register page to /register
For example
FROM
http://example.com/wp-login.php?action=register
TO
http://example.com/register/
This allows you to create a register page using a third-party forms tool such as Gravity Forms and run it from a standard WordPress page.
If you’re not sure where to place this code I highly recommend you read How to create a WordPress plugin for your custom functions.
add_action( 'login_form_register', 'redirect_login_form_register' ); function redirect_login_form_register(){ wp_redirect( home_url( '/register/' ) ); exit(); // always call `exit()` after `wp_redirect` }