Site Migration
A site migration in SEO is any substantial change to a website that can materially alter its search visibility — a new domain, new URL structure, new CMS, new design, new protocol (HTTPS), or any combination. The term is broader than "moving hosts": from Google's perspective, a migration is anything that makes URLs, HTML, or access patterns change at scale.
A site migration in SEO is any substantial change to a website that can materially alter its search visibility — a new domain, new URL structure, new CMS, new design, new protocol (HTTPS), or any combination. The term is broader than "moving hosts": from Google's perspective, a migration is anything that makes URLs, HTML, or access patterns change at scale.
Why It Matters
Migrations are the single most common cause of self-inflicted SEO disasters. Industry surveys consistently show 30–50% of site migrations cause measurable traffic drops, and 10–20% never fully recover. The biggest wins compound — a clean migration preserves the entity equity a domain has taken years to build. The biggest losses are brutal — a bungled migration can cost six-figure monthly revenue overnight and take quarters to claw back. A methodical pre/during/post checklist is the difference between the two outcomes.
Types of Site Migration
Domain migration: example.com → newbrand.com. The highest-risk category. Requires 301 redirects on every URL.
URL structure migration: /products/abc → /shop/abc. Often runs together with a CMS change.
Platform / CMS migration: WordPress → Shopify, custom → Webflow. Templates change; URLs often change too.
Protocol migration: HTTP → HTTPS. Low-risk if done right, disastrous if mixed-content errors appear.
Design / redesign: Same URLs, new HTML, different internal linking, different content depth.
Subdomain ↔ subfolder: blog.example.com ↔ example.com/blog. Both work for SEO but migrating between them must preserve links.
Internationalization: Adding or restructuring hreflang and country subdirectories.
Pre-Migration Checklist
Full URL crawl of the current site: Screaming Frog or Sitebulb. Capture every indexed URL, its traffic, and inbound links.
Map old → new URLs: A spreadsheet with current URL, new URL, status, redirect type. Every indexed URL needs a destination.
Audit backlinks: Identify the pages with the most external links. These must retain their redirects even if the rest of the site is pruned.
Benchmark baseline metrics: Rankings, GSC impressions, organic traffic, indexed pages, Core Web Vitals. You need a before picture to measure loss or gain.
Stage the new site: Crawl it on a dev domain. Fix broken links, missing canonicals, and new-structure errors before go-live.
Communicate with stakeholders: Legal, marketing, email, paid ads all depend on URL stability. Surprise migrations break everything.
Go-Live Checklist
301 redirects live before cutover: Every old URL 301s to its mapped new URL, including deeply buried category pages.
Update canonical tags to new URLs.
Submit new sitemap to Google Search Console.
Update robots.txt — don't block the new site, don't leave the old block in place.
Monitor 404s and redirect chains hourly for the first 24 hours.
Watch Core Web Vitals — a platform change often affects LCP and INP silently.
Keep old sitemap accessible for at least a few weeks so Google can discover the redirects.
Post-Migration Monitoring
Week 1: Crawl errors, 404s, redirect loops, sudden ranking drops. Compare GSC coverage reports daily.
Month 1: Index coverage, ranking changes, traffic delta vs baseline. Expect a temporary dip; it should stabilize.
Quarter 1: Final recovery assessment. If traffic isn't back to baseline within 8–12 weeks, something is structurally wrong.
Common Mistakes
302 instead of 301: 302 is temporary; Google doesn't pass full signals. Use 301.
Redirect chains: Old → intermediate → new burns crawl budget and bleeds signal. Redirect directly to the final URL.
Losing internal links: New templates often drop the old internal link graph. Re-audit after launch.
Forgetting sitemap updates: Google keeps crawling the old URLs until you tell it otherwise.
Skipping staging crawl: Problems found in production are 10× harder to fix.
No rollback plan: If the new site breaks, you need a tested path back to the old one, at least for the first 48 hours.
Quiet migrations: Announcing the migration to Google Search Console via the Change of Address tool (for domain moves) helps Google recognize the move.
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