Drupal 9 - First step after installation.
When you install Drupal, the first user that is created becomes the administrator of the site.
Drupal CMS allows you site to be capable of handling multiples user. By default the user registration is open (though administrators approval is required) and any one can register as a user for you site.
During the deployment and development of the site usually we should disable this and new account creation should only be available to administrator. Later on you can modify this setting accordingly.
That's it your site is now safe from spam registrations.
Check out the following video for demo: