What is WordPress Multisite / Network?

WordPress Multisite is a built in feature available since WordPress 3.0 (June 2010) that lets one WordPress installation host many independent sites under one codebase, one database and one user table. Each site in the network gets its own URL (subdomain or subdirectory), its own posts, its own media library and its own settings, but they all share the same plugins, themes and WordPress core files. A Super Admin manages the whole network, while regular admins only see their own site. Multisite powers WordPress.com, university websites, franchise networks and SaaS platforms where one operator runs hundreds or thousands of sites efficiently.

How does WordPress Multisite differ from a normal installation?

A standard WordPress install has one site, one set of users and one wp_options table. Multisite adds a network layer on top: the database gets extra tables (wp_blogs, wp_site, wp_sitemeta, wp_signups, wp_registration_log) and every new site gets its own numbered set of tables like wp_2_posts, wp_2_options, wp_3_posts, wp_3_options. The wp_users and wp_usermeta tables stay shared, so one account can have different roles on different sites.

Subdomain or subdirectory: which structure should I choose?

• Subdomain network (site1.example.com, site2.example.com) needs a wildcard DNS record (*.example.com) and wildcard SSL certificate. Good for separate brands or tenants.
• Subdirectory network (example.com/site1, example.com/site2) needs no DNS changes. Good for departments, languages or product lines under one brand. Cannot be chosen if the install is older than 30 days unless you patch wp-config.php.
• Domain mapping via the core feature WP_ALLOW_MULTISITE plus a plugin like Mercator or the built in mapping since WordPress 4.5 lets each site use its own top level domain (customer1.com, customer2.de).

How do I enable Multisite on an existing WordPress install?

1. Deactivate all plugins.
2. Add define('WP_ALLOW_MULTISITE', true); to wp-config.php above the "That is all, stop editing" line.
3. Open Tools » Network Setup in the admin and choose subdomain or subdirectory.
4. Copy the generated wp-config.php and .htaccess snippets WordPress shows you.
5. Log in again. You now see My Sites » Network Admin in the top toolbar.

What are typical use cases for Multisite?

• Universities with one site per department or faculty (Harvard, MIT, TU Berlin).
• Franchises and chains with one site per location (restaurants, gyms, dealerships).
• SaaS platforms like Edublogs (~5 million sites), Reclaim Hosting or CampusPress.
• Agencies managing many small client sites with shared plugin licenses.
• Multilingual setups with one site per language (alternative to Polylang or WPML).
• Staging and production as two sites in one network.

What are the advantages of Multisite?

• One WordPress core, one wp-content folder, one set of plugin updates for all sites.
• Shared user table: single sign on across all sites in the network.
• Network wide plugins (activated by Super Admin) cannot be deactivated by site admins.
• Lower hosting cost compared to running 100 separate installs.
• Central backup of one database covers all sites.

What are the disadvantages and risks of Multisite?

• Single point of failure: one core update or one bad plugin can break every site in the network.
• Shared resources: a traffic spike on one site slows down all others on the same server.
• Plugin compatibility: not every plugin is Multisite aware. WooCommerce works but is officially recommended as one shop per install. Yoast SEO, Wordfence and Elementor work network wide. ManageWP, BackupBuddy and some caching plugins behave differently.
• Migration is hard: moving one site out of a network into its own install requires manual database surgery or a paid tool like WP Migrate DB Pro.
• No per site plugin install: only Super Admin can install plugins and themes. Site admins can only activate what is already there.
• Domain mapping complexity: certificates, DNS and HTTPS redirects need careful setup.

How are users and roles handled in a network?

A user is created once in wp_users. They can be added to multiple sites with different roles (Author on site A, Editor on site B). The new role Super Admin exists only in Multisite and has full control over the network including creating sites, installing plugins, editing themes and managing all users. By default, site admins cannot install new plugins or themes; only the Super Admin can. This can be opened up via Network Admin » Settings » Network Settings » Menu Settings.

Multisite vs separate WordPress installs: when to use which?

How do I check if a site runs on Multisite?

In PHP code: is_multisite() returns true on any site inside a network. In the database, the constant MULTISITE is defined as true in wp-config.php. The presence of the tables wp_blogs, wp_site and wp_sitemeta also confirms it. Externally, a Multisite is often recognizable by URL patterns like /sites/2/files/ in image paths, since Multisite stores uploads under wp-content/uploads/sites/{blog_id}/ instead of the single site folder wp-content/uploads/YYYY/MM/.

How does InspectWP help with Multisite?

InspectWP detects WordPress Multisite installations automatically by analyzing upload URL patterns, response headers and signatures in the HTML source. The report flags whether the analyzed URL is part of a network, which simplifies audits for agencies and hosters managing many sites.