Website migrations are challenging enough with a single domain, but when multiple subdomains are involved, the complexity increases exponentially. At POLARIS, we’ve guided clients through these intricate migrations whilst preserving—and often improving—their search visibility. This guide shares our proven approach to managing SEO migrations across multiple subdomains effectively.
Understanding Subdomains and SEO
What are Subdomains and How Do They Impact SEO?
Subdomains function as distinct sections of your website that search engines treat as separate entities. Unlike subdirectories that inherit authority from your main domain, search engines crawl and index subdomains independently, assigning them their own domain authority scores. This separation makes migrating content across subdomains particularly challenging from an SEO perspective, as each subdomain has its own ranking factors and optimisation requirements.
When planning migrations involving multiple subdomains, it’s crucial to understand that simply moving content between them isn’t a straightforward process. Each subdomain’s SEO equity must be carefully preserved through strategic planning and technical implementation. This fundamental understanding forms the foundation for an effective multi-subdomain migration strategy.
Pre-Migration Planning and Strategy
Identify Strategy and Scope for Migrating a Website
A successful subdomain migration begins with clearly defined objectives. Define precisely why you’re undertaking this migration—whether it’s consolidating resources, improving user experience, or implementing a new content strategy. Evaluate potential risks specific to subdomain migrations, such as the possibility of losing subdomain-specific authority or creating confusion in search engine indexing.
Identify all stakeholders involved in the process, from technical teams managing redirects to content specialists ensuring consistent messaging across subdomains. Develop a clear architectural plan for your new subdomain structure that prioritises both user experience and search engine crawlability.
Develop a Pre-Launch Strategy for Key Pages
Not all pages carry equal SEO weight across your subdomains. Identify high-priority pages based on traffic volumes, inbound link profiles, and conversion metrics. These pages require special attention during migration to preserve their search visibility. Plan 301 redirects meticulously for these pages, especially when moving content between different subdomains.
Review the meta information and internal linking structure of these key pages, ensuring they maintain their relevance in the new subdomain architecture. Consider creating content transition plans for pages with significant rankings to ensure their authority transfers smoothly to their new locations.
Technical SEO Considerations for Subdomains
Internal Link Structure and Canonical Tags
The relationship between your subdomains plays a crucial role in migration success. Review your internal linking structure to ensure it logically connects content across subdomains whilst maintaining clear hierarchies. Implement canonical tags strategically to prevent duplicate content issues that commonly arise when similar content exists across multiple subdomains.
Ensure your link architecture clearly communicates to search engines the relationships between your various subdomains. This clarity helps search engines understand your site’s overall structure and appropriately distribute authority across your digital ecosystem.
SEO Friendly Design and Development
The technical foundation of your subdomains significantly impacts migration success. Implement semantically optimised HTML and clean code across all subdomains, ensuring consistency in technical implementation. Deploy structured data appropriate to each subdomain’s content focus to enhance search visibility.
Maintain consistent critical meta tags across subdomains whilst allowing for subdomain-specific optimisation where appropriate. Ensure all subdomains follow the same technical SEO best practices to facilitate smooth crawling and indexing by search engines.
Pre-Launch QA and Testing
Review All Pages and Templates for SEO Friendliness
Comprehensive quality assurance prevents post-migration issues. Use advanced crawling tools to create detailed maps of all pages and templates across your subdomains. Review these elements systematically for SEO friendliness, ensuring each subdomain maintains its optimisation integrity during migration.
Test not only the functionality but also the search performance implications of new templates and page designs. Pay particular attention to how content renders across devices, as mobile optimisation remains a critical ranking factor across all subdomains.
Block Search Engines from Crawling the New Site During Testing
Preventing premature indexing protects your migration from potential ranking issues. Implement robust protective measures using robots.txt files to block search engines from crawling your subdomains during the development and testing phases. Verify these blocking mechanisms work correctly through testing.
Consider implementing password protection for staging environments to provide an additional layer of security against accidental indexing. This protection is particularly important when testing redirects between subdomains, as premature implementation can create confusion in search engine indexes.
Launch Day Tasks and Action Items
Transfer All Metadata and Implement Redirects
The moment of migration requires precise execution of previously planned technical elements. Transfer all metadata from old subdomain structures to new ones, ensuring no critical SEO elements are lost in the process. Implement the prepared 301 redirects between subdomains according to your redirect mapping.
Verify all new subdomain URLs are crawlable and indexable by search engines once launched. Test redirects thoroughly to ensure they function correctly across different user entry points and referral paths.
Check Robots.txt File and Server Response
Server configuration plays a vital role in migration success. Review robots.txt files across all subdomains to ensure they now allow appropriate crawling post-launch. Test server responses for key pages on each subdomain to verify they return correct status codes.
Use Google Search Console to monitor each subdomain’s crawl status immediately after launch. Address any server-level issues promptly to prevent long-term indexing problems across your subdomain ecosystem.
Post-Launch Monitoring and Maintenance
Set Up Google Search Console for Subdomains
Individual monitoring of each subdomain provides crucial performance insights. Establish separate Google Search Console properties for each subdomain to track their individual performance. Monitor subdomain-specific crawl errors and indexing issues as they arise.
Pay particular attention to how search engines are interpreting the relationships between your subdomains. Address any unexpected indexing behaviours promptly to prevent long-term visibility issues.
Monitor Website Migration SEO Performance
Data-driven performance tracking enables timely interventions. Establish comprehensive monitoring across all subdomains using Google Analytics and rank tracking tools. Track subdomain-specific metrics including organic traffic, rankings, and conversion rates to identify any areas requiring attention.
Compare post-migration performance against your pre-migration baseline data to quantify the migration’s impact. Identify any subdomains experiencing unexpected performance changes and prioritise optimisation efforts accordingly.
Post-Launch Monitoring and Maintenance
Set Up Google Search Console for Subdomains
Individual monitoring of each subdomain provides crucial performance insights. Establish separate Google Search Console properties for each subdomain to track their individual performance. Monitor subdomain-specific crawl errors and indexing issues as they arise.
Pay particular attention to how search engines are interpreting the relationships between your subdomains. Address any unexpected indexing behaviours promptly to prevent long-term visibility issues.
Monitor Website Migration SEO Performance
Data-driven performance tracking enables timely interventions. Establish comprehensive monitoring across all subdomains using Google Analytics and rank tracking tools. Track subdomain-specific metrics including organic traffic, rankings, and conversion rates to identify any areas requiring attention.
Compare post-migration performance against your pre-migration baseline data to quantify the migration’s impact. Identify any subdomains experiencing unexpected performance changes and prioritise optimisation efforts accordingly.
SEO Migration Best Practices
Use Google Search to Test and Validate the New Site
Direct search testing provides real-world validation of your migration. Perform targeted Google searches for key content across your subdomains to verify they appear appropriately in search results. Test how Google displays your subdomain relationships in search results, particularly for branded terms.
Use Google Search Console’s URL inspection tool to diagnose specific indexing issues across your subdomain structure. Verify that search engines are correctly interpreting the canonical relationships between similar content across different subdomains.
Measuring Success and ROI
Calculate ROI and Adjust Strategy Accordingly
Quantifying migration success guides ongoing optimisation efforts. Calculate the return on investment for your subdomain migration by comparing pre- and post-migration performance metrics. Consider both direct costs and opportunity costs in your ROI calculations.
Adjust your subdomain strategy based on performance data, potentially consolidating underperforming subdomains or expanding successful ones. Continuously monitor and refine your approach to maximise the long-term SEO value of your subdomain architecture.
Managing SEO migrations across multiple subdomains requires meticulous planning, technical precision, and ongoing performance monitoring. By following this comprehensive approach, you can minimise disruption to your search visibility whilst positioning your digital ecosystem for future growth.
At POLARIS, our team of SEO migration specialists has extensive experience guiding organisations through complex subdomain migrations. Contact us today to discuss how we can help ensure your next subdomain migration enhances rather than hinders your digital performance.
