WordPress Multisite Setup and Management: Complete Enterprise Guide 2025

Q: Can I convert an existing single site to Multisite?

Yes, but make a backup first. The process modifies core files and database structure.

Q: What's the maximum number of sites?

No hard limit, but performance degrades beyond 1,000 sites without optimization. I've managed networks with 5,000+ sites using Redis, load balancers, and read replicas.

Q: Can each site have different plugins?

Yes, but all plugins must be installed in /wp-content/plugins/. Site admins can activate available plugins.

Q: Can I charge users for sites?

Yes, build custom registration + payment integration. Check out plugins like WP Ultimo.

Q: Can I restrict storage per site?

No built-in functionality. Use custom code or plugins to monitor and limit uploads.

Q: Should I use Multisite or manage separate installs?

Use Multisite if: - Sites share themes/plugins/branding - Central management needed - 10+ sites Use separate installs if: - Sites are completely different - Maximum isolation required - Clients need full access

I've deployed WordPress Multisite networks for universities with 500+ subsites, agencies managing 100+ client sites, and SaaS platforms serving thousands of users. In this guide, I'll share everything you need to know to set up, configure, and manage production-ready WordPress Multisite networks.

What is WordPress Multisite?

WordPress Multisite turns a single WordPress installation into a network of sites sharing:

Single WordPress codebase (core, themes, plugins)
Single database (with separate tables for each site)
Centralized administration (network admin dashboard)
Shared resources (media, users, configurations)

Think of it like Gmail: one platform, millions of individual accounts.

When to Use WordPress Multisite

Good Use Cases

✅ Agency managing client sites: 50+ client sites, shared themes/plugins, central billing ✅ University network: Department sites, course sites, faculty blogs ✅ SaaS platforms: User-generated sites (like WordPress.com) ✅ Corporate intranet: Department sites, regional offices ✅ Franchise websites: Shared branding, location-specific content ✅ Multi-language sites: Separate site per language

When NOT to Use Multisite

❌ Single site with multiple authors: Just use WordPress roles ❌ Completely different sites: No shared themes/plugins/branding ❌ Client sites requiring isolation: Separate installs for security ❌ Small networks (< 5 sites): Overhead not worth it

I worked with an agency that prematurely adopted Multisite for 5 client sites. The complexity outweighed benefits. Once they hit 25+ sites, Multisite became valuable.

Multisite Architecture Overview

Subdomain vs Subdirectory

Subdomain setup:

main-site.com (network home)
site1.main-site.com
site2.main-site.com
site3.main-site.com

Subdirectory setup:

main-site.com (network home)
main-site.com/site1
main-site.com/site2
main-site.com/site3

Domain mapping (advanced):

main-site.com (network home)
client1.com → site1.main-site.com
client2.com → site2.main-site.com

Database Structure

Single database with prefixed tables per site:

wp_posts                (site 1 - main site)
wp_postmeta
wp_users                (shared across network)
wp_usermeta
wp_blogs                (list of all sites)
wp_sitemeta             (network-wide settings)

wp_2_posts              (site 2)
wp_2_postmeta
wp_2_options

wp_3_posts              (site 3)
wp_3_postmeta
wp_3_options

Setting Up WordPress Multisite

Prerequisites

Fresh WordPress installation (or backup existing site)
Apache or Nginx with mod_rewrite
PHP 7.4+ recommended
MySQL 5.7+ or MariaDB 10.3+
SSL certificate (recommended)
Access to wp-config.php and .htaccess

Step 1: Backup Everything

CRITICAL: Backup before enabling Multisite (it modifies core files and database).

# Backup files
tar -czf wordpress-backup-$(date +%Y%m%d).tar.gz /path/to/wordpress

# Backup database
mysqldump -u username -p database_name > db-backup-$(date +%Y%m%d).sql

Step 2: Deactivate All Plugins

Plugins can interfere with Multisite activation.

# Via WP-CLI (fastest)
wp plugin deactivate --all

# Or manually in WordPress dashboard:
# Plugins → Installed Plugins → Deactivate All

Step 3: Enable Multisite in wp-config.php

Add above /* That's all, stop editing! */ line:

/* Multisite */
define('WP_ALLOW_MULTISITE', true);

Save and refresh WordPress dashboard. You'll see:

Tools → Network Setup

Step 4: Configure Network

Visit Tools → Network Setup and choose:

Subdomain or Subdirectory structure
Network Title (e.g., "My Network")
Network Admin Email

Click Install.

Step 5: Update wp-config.php

WordPress will provide code to add to wp-config.php. Example:

define('MULTISITE', true);
define('SUBDOMAIN_INSTALL', true); // false for subdirectory
define('DOMAIN_CURRENT_SITE', 'your-domain.com');
define('PATH_CURRENT_SITE', '/');
define('SITE_ID_CURRENT_SITE', 1);
define('BLOG_ID_CURRENT_SITE', 1);

Add above /* That's all, stop editing! */ line.

Step 6: Update .htaccess (Apache)

Replace existing WordPress rules with:

RewriteEngine On
RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]
RewriteBase /
RewriteRule ^index\.php$ - [L]

# add a trailing slash to /wp-admin
RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(wp-(content|admin|includes).*) $2 [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(.*\.php)$ $2 [L]
RewriteRule . index.php [L]

Step 7: Configure DNS (for Subdomains)

If using subdomain structure:

Add wildcard DNS record in your domain registrar:

Type: A
Name: *
Value: Your server IP address
TTL: 3600

This allows any subdomain (site1.yourdomain.com, site2.yourdomain.com) to work.

Step 8: Test Network

Log out and back in
You'll see My Sites in admin bar (top left)
Visit My Sites → Network Admin → Dashboard

Success! Your Multisite network is active.

Creating New Sites

Via Network Admin Dashboard

My Sites → Network Admin → Sites → Add New
Fill in:
- Site Address: subdomain or subdirectory name
- Site Title: Display name
- Admin Email: Site administrator email
Click Add Site

WordPress automatically:

Creates database tables
Sends email to site admin
Configures default theme/settings

Via WP-CLI (Faster)

# Create new site
wp site create --slug=newsite --title="New Site" --email="admin@example.com"

# Create with custom URL (domain mapping)
wp site create --slug=client1 --title="Client Site" --email="client@example.com"

# Create and assign user as admin
wp site create --slug=blog1 --title="Blog 1" --email="user@example.com" --private

Programmatically (for SaaS platforms)

function create_new_site($domain, $title, $user_id) {
    $site_id = wpmu_create_blog(
        $domain,                // e.g., 'newsite' for subdomain
        '/',                    // path (always / for subdomains)
        $title,                 // site title
        $user_id,               // admin user ID
        array('public' => 1),   // options
        1                       // network ID
    );

    if (is_wp_error($site_id)) {
        return false;
    }

    return $site_id;
}

// Usage
$new_site_id = create_new_site('johndoe', 'John Doe Blog', 5);

Network Administration

Network Admin Dashboard

Access: My Sites → Network Admin

Key sections:

Sites: Manage all sites (activate/deactivate, delete, visit)
Users: Manage network users, assign to sites
Themes: Enable themes for entire network
Plugins: Network-activate plugins
Settings: Network-wide configurations

Network-Wide vs Site-Specific

Network Admin controls:

Which themes are available
Which plugins can be activated
Default settings for new sites
User permissions

Site Admins control:

Their site content
Activating allowed themes/plugins
Site-specific settings

User Roles in Multisite

Network roles:

Super Admin: Full network control (can manage all sites)
Administrator: Full control over assigned sites

Site roles (standard WordPress):

Administrator, Editor, Author, Contributor, Subscriber

Assign user to multiple sites:

# Via WP-CLI
wp user set-role user@example.com administrator --url=site1.example.com
wp user set-role user@example.com editor --url=site2.example.com

Theme Management

Enable Themes Network-Wide

Network Admin → Themes
Hover over theme → Network Enable
Site admins can now activate it on their sites

Network-activate (all sites use theme):

Rare use case
Enforces consistent branding

Allow Site Admins to Choose Themes

Default behavior: Site admins see enabled themes and can activate/switch freely.

Restrict Theme Access

// Only allow specific themes for non-super admins
function restrict_themes_for_sites($themes) {
    if (is_super_admin()) {
        return $themes;
    }

    $allowed = array('twentytwentyfour', 'my-custom-theme');

    foreach ($themes as $theme_key => $theme) {
        if (!in_array($theme_key, $allowed)) {
            unset($themes[$theme_key]);
        }
    }

    return $themes;
}
add_filter('wp_prepare_themes_for_js', 'restrict_themes_for_sites');

Plugin Management

Network Activation

Network Admin → Plugins → Network Activate

Plugin runs on all sites. Site admins cannot deactivate.

Use for:

Security plugins (Wordfence, iThemes Security)
Backup plugins
Performance plugins (caching)
Essential functionality

Allow Site-Level Activation

Upload plugin to /wp-content/plugins/
Don't network-activate
Site admins can activate on their sites

Must-Use Plugins (mu-plugins)

Automatically loaded on all sites, cannot be deactivated.

Create: /wp-content/mu-plugins/my-custom-functionality.php

<?php
/**
 * Plugin Name: Network Custom Functionality
 * Description: Must-use plugin for network-wide features
 */

// Example: Disable comments network-wide
add_action('admin_init', function() {
    // Remove comments menu
    remove_menu_page('edit-comments.php');
});

// Example: Custom dashboard widget for all sites
add_action('wp_dashboard_setup', function() {
    wp_add_dashboard_widget(
        'network_info',
        'Network Information',
        function() {
            echo '<p>You are part of our network!</p>';
        }
    );
});

Domain Mapping

Give each site a custom domain (e.g., client1.com instead of client1.network.com).

Method 1: WordPress Plugin (Easier)

Recommended: Mercator (free, by Human Made)

Install Mercator via Composer or manually

Add to wp-content/sunrise.php:

<?php
require_once WP_CONTENT_DIR . '/plugins/mercator/sunrise.php';

Add to wp-config.php:
```
define('SUNRISE', true);
```
Configure DNS:
- Point client1.com A record to your server IP
- Add domain in Mercator settings for each site

Method 2: Manual Server Configuration (Advanced)

Configure Nginx/Apache to route domains to specific subsites.

Nginx example:

server {
    listen 80;
    server_name client1.com;

    root /var/www/html;
    index index.php;

    location / {
        try_files $uri $uri/ /index.php?$args;
    }

    location ~ \.php$ {
        fastcgi_pass unix:/run/php/php8.1-fpm.sock;
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
        include fastcgi_params;
    }
}

Performance Optimization

1. Object Caching (Critical)

Without object caching, Multisite performance degrades quickly.

Install Redis or Memcached:

# Install Redis
sudo apt install redis-server php-redis

# Enable Redis Object Cache
wp plugin install redis-cache --activate --network
wp redis enable

Impact: Reduces database queries by 50-80%.

2. Optimize Database

Large networks accumulate bloat fast.

-- Clean up spam/trashed posts across all sites
DELETE FROM wp_posts WHERE post_status = 'trash';
DELETE FROM wp_2_posts WHERE post_status = 'trash';
-- Repeat for each site (wp_3_posts, wp_4_posts, etc.)

-- Or use WP-CLI to clean all sites:
wp site list --field=url | xargs -I {} wp post delete $(wp post list --post_status=trash --format=ids --url={}) --force

3. Limit Post Revisions

Add to wp-config.php:

define('WP_POST_REVISIONS', 3); // Limit to 3 revisions per post

4. Use CDN for Shared Assets

Offload uploads, themes, plugins to CDN:

// In wp-config.php
define('WP_CONTENT_URL', 'https://cdn.yournetwork.com/wp-content');

5. Separate Uploads Directory (Optional)

For large networks, separate media uploads:

// In wp-config.php
define('UPLOADS', 'wp-content/uploads');
define('BLOGUPLOADDIR', '/path/to/shared-uploads/');

Security Considerations

1. Limit Network Admin Access

Only trusted users should have Super Admin role.

// Remove super admin privileges
remove_role_from_user(1, 'super_admin');

// Grant super admin (use sparingly)
grant_super_admin(1); // User ID

2. Restrict Plugin/Theme Installation

By default, site admins cannot install plugins/themes. Keep it that way unless necessary.

To allow (not recommended):

// In wp-config.php (use with caution)
define('ALLOW_SITE_ADMIN_TO_MANAGE_THEMES', true);

3. Isolate Sites (Database Security)

Use separate database users per site for high-security scenarios:

// In wp-config.php
if (defined('BLOG_ID_CURRENT_SITE')) {
    if (BLOG_ID_CURRENT_SITE == 2) {
        define('DB_USER', 'site2_user');
        define('DB_PASSWORD', 'site2_password');
    } elseif (BLOG_ID_CURRENT_SITE == 3) {
        define('DB_USER', 'site3_user');
        define('DB_PASSWORD', 'site3_password');
    }
}

4. Monitor Disk Usage

Users uploading large files can exhaust server storage.

Limit upload sizes per site:

// In functions.php of network-activated plugin
function limit_upload_size($size) {
    return 10 * 1024 * 1024; // 10 MB max
}
add_filter('upload_size_limit', 'limit_upload_size');

Monitor disk usage:

# Check uploads directory size per site
du -sh /var/www/html/wp-content/uploads/sites/*

Useful Multisite Plugins

Network Management:

Multisite Enhancements - Improved network admin UI
WP Multi Network - Networks within networks

Domain Mapping:

Mercator - Modern domain mapping

User Management:

User Switching - Switch between user accounts
Multisite User Management - Bulk user operations

Content Sharing:

Multisite Post Duplicator - Copy posts between sites

Monitoring:

MainWP - Manage network from external dashboard

WP-CLI for Multisite

Essential commands:

# List all sites
wp site list

# Create new site
wp site create --slug=newsite --title="New Site"

# Delete site
wp site delete 5 --yes

# Empty site (delete all content)
wp site empty 5 --yes

# Archive/unarchive site
wp site archive 5
wp site unarchive 5

# Network-activate plugin
wp plugin activate plugin-name --network

# Update all sites
wp site list --field=url | xargs -I {} wp core update --url={}

Common Issues and Solutions

Issue 1: Subdomains Not Working

Cause: Missing wildcard DNS or mod_rewrite

Fix:

Verify wildcard DNS: dig site1.yourdomain.com
Check mod_rewrite enabled: apache2ctl -M | grep rewrite
Verify .htaccess rules

Issue 2: 404 Errors on Subsites

Cause: Incorrect permalink structure

Fix:

Visit Network Admin → Settings
Save settings (refreshes permalinks)
Visit individual site → Settings → Permalinks → Save

Issue 3: Slow Network Admin Dashboard

Cause: Large number of sites without object caching

Fix: Install Redis (shown earlier)

Issue 4: Email Not Sending

Cause: Shared server limits, SPF/DKIM not configured

Fix: Use SMTP plugin (WP Mail SMTP)

Migration Strategies

Migrate Existing Sites to Multisite

Backup all sites
Set up fresh Multisite network
Use migration plugin:
- Multisite Migration
- Or All-in-One WP Migration Multisite
Or manually via WP-CLI:

# Export single site
wp db export single-site.sql --url=oldsite.com

# Import into Multisite subsite
wp db import single-site.sql --url=newsite.network.com

# Fix URLs
wp search-replace 'oldsite.com' 'newsite.network.com' --url=newsite.network.com

Migrate Multisite to Single Sites

Reverse process (split network into individual WordPress installs).

Use Multisite to Single Site plugin.

Frequently Asked Questions

Can I convert an existing single site to Multisite?