WordPress Multisite enables managing multiple websites from single WordPress installation. Networks share core files, themes, and plugins whilst maintaining separate databases for content. Professional Multisite implementations serve universities, franchises, publishing networks, and organisations requiring centralised control over multiple sites.
WordPress Multisite transforms single WordPress installations into networks of sites. One WordPress installation, one database, multiple websites.
Sites share WordPress core, themes, and plugins. Each site maintains separate content, users, and settings in distinct database tables.
Network Administrators control entire networks. Site Administrators manage individual sites within networks.
Common use cases include:
Multisite reduces maintenance overhead. Update WordPress once; all sites receive updates simultaneously.
Understanding Multisite architecture enables implementing appropriate WordPress development solutions for multi-site requirements.
Multisite setup modifies wp-config.php and .htaccess enabling network functionality. Backup before enabling Multisite as changes prove difficult reversing.
Enable Multisite:
Add to wp-config.php above "stop editing":
/* Multisite */
define('WP_ALLOW_MULTISITE', true);
Install Network:
Visit Tools > Network Setup. Choose subdomain or subdirectory structure:
Subdomain Requirements:
Wildcard DNS record: *.example.com → server IP Server configured accepting wildcard subdomains
Complete Installation:
Add generated code to wp-config.php:
define('MULTISITE', true);
define('SUBDOMAIN_INSTALL', true); // false for subdirectory
define('DOMAIN_CURRENT_SITE', 'example.com');
define('PATH_CURRENT_SITE', '/');
define('SITE_ID_CURRENT_SITE', 1);
define('BLOG_ID_CURRENT_SITE', 1);
Update .htaccess with generated rules.
Access Network Admin:
Navigate to My Sites > Network Admin. Control entire network from centralised dashboard.
Multisite setup requires careful configuration. Test on staging environments before production deployment.
Multisite architecture combines shared resources with isolated content ensuring efficient resource usage whilst maintaining site independence.
Shared Resources:
Isolated Resources:
Database Structure:
wp_blogs - Site registry
wp_blogmeta - Site metadata
wp_site - Network information
wp_sitemeta - Network settings
wp_users - Network-wide users
wp_usermeta - User metadata
wp_2_posts - Site 2 posts
wp_2_options - Site 2 options
wp_3_posts - Site 3 posts
etc.
Network tables manage overall structure. Site-specific tables contain individual site data.
Understanding architecture enables efficient Multisite management and troubleshooting.
Network Administrators control settings, themes, plugins, and sites across entire networks. Centralised management provides powerful control.
Network Settings:
Configure network-wide settings:
Site Management:
Add, edit, or delete sites:
User Management:
Network users access multiple sites with assigned roles per site. Single login spans entire network.
Add users at network level. Assign to sites with appropriate roles.
Theme Management:
Install themes once for entire network. Network-activate for all sites or enable individually per site.
Site Administrators activate only network-enabled themes. Network Administrators control theme availability.
Plugin Management:
Similar to themes. Network-activate plugins running across all sites. Individually activate where needed.
Network Administrators enable plugins for sites. Site Administrators activate enabled plugins.
Centralised management reduces administrative overhead across large site networks.
Choose between subdomain or subdirectory structure based on requirements and technical constraints.
Subdomain Multisite:
site1.example.com
site2.example.com
blog.example.com
Advantages:
Requirements:
Subdirectory Multisite:
example.com/site1/
example.com/site2/
example.com/blog/
Advantages:
Limitations:
Domain Mapping:
Map custom domains to network sites. WordPress 4.5+ includes domain mapping core.
site1.com → site1.example.com
site2.com → site2.example.com
Custom domains provide complete branding independence whilst maintaining centralised management.
Choose structure based on branding requirements, technical capabilities, and future scalability needs.
Multisite networks require vigilant security. Compromise of one site potentially affects entire network.
Network-Level Security:
Limit network administrator access. Elevated privileges require trust.
Enforce strong passwords across network. Implement two-factor authentication.
Restrict plugin/theme uploads. Malicious code uploaded affects entire network.
Site Isolation:
While sharing code, sites remain logically separated. Database tables prevent cross-site data access.
However, server-level vulnerabilities potentially expose entire network.
Plugin/Theme Vetting:
Carefully review code before network activation. Vulnerable plugins compromise all sites.
Limit site-activated plugins. Prevent site administrators installing risky plugins.
Regular Updates:
Update WordPress core affecting all sites simultaneously. Timely updates essential.
Test updates on staging networks before production deployment.
Backup Strategy:
Backup entire network including all site databases. Network failure requires complete restoration.
Implement automated backups with offsite storage.
User Management:
Regularly audit network users. Remove inactive accounts preventing unauthorised access.
Monitor user role assignments ensuring appropriate permissions.
Multisite security requires comprehensive WordPress security practices applied network-wide.
Multisite performance requires optimising shared resources whilst managing multiple site loads.
Caching Strategies:
Object caching benefits networks significantly. Redis or Memcached cache database queries across sites.
Page caching per site. Configure caching respecting site-specific content.
Database Optimisation:
Regular database optimisation maintains performance. Multisite databases grow quickly with multiple sites.
Implement query monitoring identifying slow queries across network.
CDN Integration:
CDN distribution essential for multisite. Static assets serve from edge servers globally.
Configure CDN respecting site-specific media.
Resource Limits:
Impose resource limits preventing single sites overwhelming servers. Disk quotas, upload limits, and memory restrictions.
Monitor resource usage identifying problematic sites.
Efficient Queries:
Avoid querying across sites. Cross-site queries exponentially increase database load.
Cache results when cross-site data necessary.
Theme/Plugin Efficiency:
Lightweight themes and plugins benefit entire network. Bloated code slows all sites.
Audit active plugins removing unnecessary extensions.
Network performance directly impacts all sites. Optimise comprehensively.
Combine Multisite optimisation with WordPress speed optimisation achieving maximum performance.
When should I use WordPress Multisite?
Use Multisite when managing multiple related sites requiring centralised control. Universities with departmental sites, franchises with location sites, or agencies managing client sites benefit from Multisite. Avoid Multisite for unrelated websites, when sites require different WordPress versions, or when complete independence needed. Evaluate whether centralised management benefits justify Multisite complexity versus managing separate WordPress installations.
Can I convert existing WordPress sites to Multisite?
Yes, convert existing sites to Multisite through migration plugins or manual database imports. However, conversion complexity often exceeds starting fresh. Export content from existing sites, enable Multisite on new installation, create network sites, then import content. Test thoroughly as conversions sometimes create unexpected issues. Evaluate whether conversion benefits justify migration effort versus maintaining separate installations.
Does Multisite affect SEO?
Multisite architecture itself doesn't harm SEO. Subdomains create separate domains search engines treat independently. Subdirectories consolidate domain authority benefiting overall SEO. Domain mapping enables custom domains maintaining independent SEO profiles. Implement proper WordPress SEO practices per site. Content quality and optimisation matter more than Multisite architecture for SEO success.
How many sites can Multisite handle?
Properly configured Multisite networks handle thousands of sites. WordPress.com runs millions of sites on Multisite. Practical limits depend on hosting resources, traffic, and content. Shared hosting handles 5-20 sites. VPS hosting manages 50-100 sites. Dedicated servers support 100-1000+ sites. Database size, server resources, and traffic determine practical limits. Optimise infrastructure as networks grow.
Can Multisite sites have different themes?
Yes, sites within networks use different themes. Network Administrators enable themes network-wide. Site Administrators activate any enabled theme for their sites. This flexibility enables maintaining brand consistency across some sites whilst allowing variation on others. Theme selection control provides valuable flexibility for organisations managing diverse site portfolios within single networks.
Is Multisite hosting more expensive?
Multisite hosting costs similar to single-site hosting initially but scales more cost-effectively. One WordPress installation serves multiple sites reducing per-site costs. However, Multisite requires robust hosting handling multiple sites' combined load. Shared hosting struggles with Multisite; VPS or dedicated hosting recommended. While individual hosting costs more, per-site economics favour Multisite for organisations managing numerous sites.
Can I use different plugins on different Multisite sites?
Yes, with caveats. Network Administrators control which plugins Site Administrators can activate. Network-activated plugins run across all sites. Individually-activated plugins run only on enabling sites. This provides flexibility whilst maintaining central control. However, all plugins must install at network level; Site Administrators cannot upload plugins. Balance flexibility against security and management efficiency.
Related WordPress Development Topics:
Written by the WordPress Development Team at London Web Design, managing Multisite networks for London organisations since 2012.
