WordPress Multisite Guide: Run a Network of Sites Like a Pro

Open your wp-config.php file and add the following line above the "That's all, stop editing!" comment:

define( 'WP_ALLOW_MULTISITE', true );

After saving wp-config.php, go to Tools → Network Setup in your WordPress admin. Choose between subdomains or subdirectories and set your network title.

WordPress will generate code snippets. Add the Multisite constants to wp-config.php:

define( 'MULTISITE', true );
define( 'SUBDOMAIN_INSTALL', false ); // true for subdomains
define( 'DOMAIN_CURRENT_SITE', 'example.com' );
define( 'PATH_CURRENT_SITE', '/' );
define( 'SITE_ID_CURRENT_SITE', 1 );
define( 'BLOG_ID_CURRENT_SITE', 1 );

Replace your existing rewrite rules with the ones WordPress provides. For Nginx, you'll need to add specific location blocks for the Multisite URL structure.

Log back in (you'll be redirected). You'll now see a "My Sites" menu and "Network Admin" dashboard. Configure: Network Settings, default theme, registration settings, and upload limits.

Go to Network Admin → Sites → Add New. Enter the site address, title, and admin email. The site is instantly live with your default theme.

Plugin Compatibility

Not all plugins work with Multisite. Before installing, check:

Install Redis or Memcached. Without object caching, every page load queries the database for site-specific options. With 20+ sites, this crushes performance. Redis is preferred, it handles Multisite's wp_X_options table lookups efficiently.

Use Cloudflare or a CDN that supports wildcard domains. Each sub-site generates its own static assets, without a CDN, your server handles every CSS, JS, and image request across all sites.

Each Multisite sub-site creates 10+ database tables. A 50-site network has 500+ tables. Run regular optimization: remove revisions, clean transients, and consider database table partitioning for large networks.

Multisite needs more PHP workers than a single site. Rule of thumb: 2 PHP workers per actively-trafficked site. A 10-site network needs at minimum 8-12 PHP workers. Budget hosting (2-4 workers) will cause timeout errors.

❌ Using shared hosting for 10+ sites

✅ Multisite needs dedicated resources. Use VPS or managed WordPress hosting with guaranteed PHP workers.

❌ Not planning the URL structure first

✅ You can't switch between subdomains and subdirectories after setup without starting over. Decide before installing.

❌ Giving too many people Super Admin

✅ Super Admin can delete any site, install any plugin, and access any dashboard. Limit to 1-2 people maximum.

❌ Network Activating every plugin

✅ It forces plugins on all sites. Only Network Activate truly universal plugins (security, caching). Let site admins choose the rest.

❌ Skipping object caching

✅ Without Redis/Memcached, database queries multiply with each site. Object caching is not optional for networks over 5 sites.

❌ No network-wide backup strategy

✅ Standard backup plugins often miss Multisite tables. Use BlogVault, UpdraftPlus Premium, or ManageWP for proper network backups.