WordPress Multisite is a built-in feature that allows you to run multiple, separate websites from a single WordPress installation via a shared administration interface, using a shared set of themes and plugins.

How does it work?

The multisite network is managed by the super administrator (Super Admin): they install themes and plugins, and create new sites and users. The administrators of individual sites only manage the content and settings of their own site, and can only choose from the themes and plugins authorised within the network.

The subpages of the network may include:

• subdomains, such as blog.pelda.hu, bolt.pelda.hu,
• subdirectories, such as pelda.hu/blog, pelda.hu/bolt,
• Custom domains (with domain mapping): since WordPress 4.5, a separate domain can be assigned to any page without the need for a plugin.

The websites store their content in a shared database but in separate tables, whilst the WordPress files, themes and plugins are shared. Therefore, it is sufficient to update WordPress and the plugins just once across the entire network.

When is it worth using multisite?

• If you operate several interlinked websites with a similar structure (e.g. websites for the brands of a group of companies or the outlets of a franchise network) and would like to manage them from a single location.
• In educational institutions, where each faculty, department or class is given its own subpage.
• For multilingual websites where each language has its own subpage.

When is it not worth it?

• If the websites are independent of one another, belong to projects with different requirements, or belong to different customers who require full administrative rights (for example, to install their own plugins).
• If you wish to perform a migration or sell the websites separately at a later date: removing a sub-site from the network is more difficult than performing a migration for a standalone installation.
• If a plugin does not support multisite, always check this before installation.

It is also important to note that a single vulnerable plugin or faulty update on the network can affect all sites simultaneously, and the load caused by one site on the network slows down the others as well, because they all run on the same hosting server.

How do I enable it?

1. Perform a full backup of your files and database.
2. Disable all plugins.
3. In the wp-config.php file, above the line /* That's all, stop editing! */, enter: define( 'WP_ALLOW_MULTISITE', true );
4. Refresh the admin interface, then open the Tools > Network Setup menu item.
5. Select either the subdomain or subdirectory structure, enter the network name and the administrator’s email address, then click the Install button.
6. Copy the code snippets displayed by WordPress into the wp-config.php and .htaccess files, then log in again.

It can be difficult to change your chosen configuration later on, so please decide in advance. For subdomain networks, the subdomains must also be added to the hosting account via cPanel; when mapping your own domains, the domains must be added as alias (parked) domains. WordPress hosting plans include varying numbers of parked and additional domains, so please bear this in mind when selecting a plan for a larger network. The article on adding domains and subdomains in cPanel explains how to add domains.