The most common option is to make the website open in the domain where it will be located.
But there are clients who don't want anyone to see it until it is completely finished.
To do this, it is recommended to indicate that the website is ig database construction, but of course, the client will only be able to see it if we give them some WordPress access keys.
If we give them to you, you should log in through username and password, you would see the administration menus, the top bar, etc… which looks horrible.

So, today we leave you the best option.
The first thing would be to install the Web Under Construction Maintenance plugin:
The good thing about this plugin is that, once installed and activated, when we enter the website we will see a little padlock on the right:
When you click on the padlock, a small window will appear asking for your username and password to view the website.
The recommendation is to register a user as a subscriber and give the client that username and password, so that they can access the website and cannot modify anything.
Now, there is a problem, and that is that the client will see the top administration bar on the web, the solution is a plugin to make it disappear called Hide Admin Bar Based on User Roles:
Hide Admin Bar Based on User Roles
As the name of the plugin suggests, it allows you to hide the admin bar from certain users based on their role. What you need to do is go to the plugin settings and tell it that you only want to hide the admin bar from the subscriber profile, which is the type of profile you have assigned to the client user.