WordPress.org

After this plugin is activated, and until it is deactivated or its main plugin file removed, site visitors will be forced to login before they will be able to see any content on the WordPress site.

If a WordPress Network is defined, the plugin can be activated individually for select sites. Or Network Activated, in which case all sites in the Network will require user login before any content will become visible.

Login prompts are provided whenever a non-logged in user ("site visitor") attempts to access any URL controlled by WordPress on the web site. This plugin does not control non-WordPress web pages, such as .html and .php files created by hand or by other software products.

Yes, there are other plugins that hide all WordPress content for any site visitor who is not logged on. But when I was searching for a solution for one of the web sites I support, I decided to "write my own" because I knew how it worked and felt comfortable that there would be no way for anyone not logged in to view the site, including Search Engines.