Migrating a single WordPress site is manageable with the right guide and a few hours of careful work. Migrating a WordPress Multisite network is an entirely different challenge. The shared database, domain mapping tables, network-level configurations, and inter-site dependencies create failure modes that don't exist in single-site migrations — and the cost of those failures affects every site in the network simultaneously, not just one.
This guide covers what makes Multisite migrations genuinely hard, the specific failure points that catch even experienced developers off guard, and the framework for deciding when professional migration services are worth the cost.
Why WordPress Multisite Migrations Are Different
Standard WordPress migration advice doesn't fully apply to Multisite. Here's what's different:
Single database, complex structure
A Multisite network stores all sites in one database, with separate table prefixes per site (wp_2_posts, wp_3_posts, etc.) plus shared network-level tables (wp_users, wp_usermeta, wp_site, wp_blogs). A search-and-replace for the old server URL affects network tables that reference individual site URLs — get this wrong and sub-sites lose their domain mapping or break their administrative URLs.
Domain mapping complexity
If your Multisite uses custom domain mapping (each sub-site has its own domain, e.g., client1.com and client2.com on the same network), each domain's DNS must be updated, each domain's SSL certificate must be issued on the new server, and the domain mapping plugin or WordPress native domain mapping must be reconfigured. Missing one domain means that client's site is broken after migration.
Plugin and theme compatibility across all sites
Plugins installed network-wide must work on the new server's PHP version and configuration. A PHP 7.4 → 8.1 upgrade as part of a server migration can break plugins that were never updated for 8.x — and because plugins are network-activated, one broken plugin can affect every site in the network.
File uploads structure
Multisite stores uploads per-site in wp-content/uploads/sites/N/ rather than the standard wp-content/uploads/. Migration tools that handle single-site uploads correctly sometimes miss this structure, leaving media libraries broken across all sub-sites.
Common Migration Mistakes That Cost Thousands
Running search-and-replace on the wrong tables
A standard WordPress search-and-replace (old URL → new URL) on a Multisite database can corrupt the wp_blogs table which stores the site URL for each sub-site, break the siteurl and home options in each site's options table, and corrupt serialised data in ways that break plugin settings across the network. The safe approach is to use WP-CLI with Multisite-aware flags:
wp search-replace 'http://oldserver.com' 'http://newserver.com' --network --skip-columns=guid --report-changed-onlyMigrating without updating wp-config.php network settings
The Multisite configuration in wp-config.php includes DOMAIN_CURRENT_SITE which must be updated to the new server's domain. Missing this causes the entire network to attempt to resolve to the old domain after migration.
define('DOMAIN_CURRENT_SITE', 'newdomain.com'); // must be updated
define('PATH_CURRENT_SITE', '/');
define('SITE_ID_CURRENT_SITE', 1);
define('BLOG_ID_CURRENT_SITE', 1);Migrating during peak traffic
Unlike single-site migrations where you can put one site in maintenance mode, Multisite maintenance mode affects all sites in the network simultaneously. Migrating during business hours means every client site shows a maintenance page at the same time.
Incomplete file permissions after migration
Multisite requires specific file permissions for the uploads directory, and some web server configurations need explicit permission for the /wp-admin/network/ path. After migration, file manager plugins and media uploads can silently fail if permissions don't match the new server's web user.
DIY vs. Professional Migration: True Cost Comparison
For a 10-site Multisite network with custom domain mapping:
DIY migration time estimate (experienced developer, no unexpected issues):
- Pre-migration audit and documentation: 2–3 hours
- Setting up and testing new server: 3–4 hours
- Database export, transfer, and import: 1–2 hours
- File transfer and permissions: 1–2 hours
- WP-CLI search-and-replace and network URL update: 1–2 hours
- DNS updates for 10 custom domains: 1–2 hours
- SSL certificate installation for each domain: 1–2 hours
- Testing all 10 sites post-migration: 2–4 hours
- Debugging unexpected issues (budget this, it almost always occurs): 2–8 hours
Total: 14–29 hours for an experienced developer. At $75/hour, that's $1,050–$2,175 in labour cost.
Professional migration cost for a 10-site Multisite: $600–$1,500 — and that includes handling the unexpected issues, verification, and post-migration monitoring.
Signs Your Multisite Network Needs Professional Migration
- More than 5 sub-sites using custom domain mapping — each domain adds migration complexity
- Active e-commerce on any sub-site — live orders during migration create data consistency problems
- You've never migrated a Multisite before — the learning curve is expensive when applied to production
- The migration involves a PHP version change — compatibility testing across all network plugins takes significant time
- Any sub-site has more than 10,000 posts or a database table over 1 GB — large databases require different handling for consistency
- Zero-downtime is required — staged migrations with traffic routing require infrastructure expertise beyond standard migration skills
What a Managed Multisite Migration Service Includes
A professional migration for WordPress Multisite should cover:
- Pre-migration audit: documenting all sub-sites, custom domains, active plugins, and database size
- New server setup and configuration: matching PHP version, web server config, and file permissions to current environment (then upgrading safely if required)
- Database migration with Multisite-aware search-and-replace — not a generic find/replace that corrupts serialised data
- Custom domain DNS update coordination — either handling DNS changes or providing the exact records to update with confirmed timing
- SSL certificate issuance and installation for every custom domain
- Post-migration testing of every sub-site — admin, front-end, media uploads, form submissions
- 48-hour monitoring period with rollback available if issues emerge
WordPress Multisite migrations done incorrectly break multiple clients' businesses simultaneously. The risk profile is fundamentally different from a single-site migration, and the cost of a failed migration — fixing broken sites for 10 clients, managing the fallout — almost always exceeds the cost of doing it right the first time with professional help.
CloudHouse Technologies handles WordPress Multisite migrations with full pre-migration audits, Multisite-aware database handling, custom domain SSL setup, and post-migration monitoring — so your entire network moves cleanly without affecting your clients.