SEO Site Migrations — Protecting Rankings
Learn how to migrate a website without losing SEO rankings. Covers migration types, redirect mapping, pre-launch testing, and post-migration monitoring.
A site migration is any significant change to a website that affects its URL structure, domain, platform, or content organisation. Migrations are the highest-risk SEO events — poorly executed migrations routinely cause 20–50% traffic drops that can take months to recover from. A well-planned migration minimises risk and can even improve organic performance.
- Site migrations include domain changes, URL restructuring, platform changes, HTTPS moves, redesigns, and content reorganisations.
- The golden rule: every old URL must redirect to its corresponding new URL via 301 redirect.
- Plan for 3–6 months of ranking fluctuation after migration — dips are normal, prolonged drops indicate problems.
- Create a complete URL mapping document before migration and test every redirect.
- Never migrate without pre-migration baseline data — you need it to measure impact.
If you want the full breakdown, continue below.
Types of Site Migration
| Migration Type | Risk Level | Example |
|---|---|---|
| Domain change | Very High | oldsite.com → newsite.com |
| Domain + URL change | Very High | oldsite.com/services/ → newsite.com/what-we-do/ |
| HTTP → HTTPS | Medium | http://site.com → https://site.com |
| URL restructure | High | /page?id=123 → /services/web-design/ |
| Platform change | High | WordPress → Next.js |
| Redesign (same URLs) | Low–Medium | New design, same URL structure |
| Subdomain change | High | blog.site.com → site.com/blog/ |
| Content reorganisation | Medium | Merging or splitting pages |
The Migration Framework
Phase 1 — Pre-Migration Planning (4–8 Weeks Before)
Baseline documentation:
- Export all current URLs (full crawl with Screaming Frog)
- Record current keyword rankings for priority keywords
- Document current organic traffic by page
- Export backlink profile with landing pages
- Screenshot key pages for reference
URL mapping:
Create a complete old-URL → new-URL mapping:
| Old URL | New URL | Status Code | Notes |
|---|---|---|---|
| /services/web-design/ | /web-design/ | 301 | URL restructure |
| /about-us/ | /about/ | 301 | Simplified URL |
| /blog/old-post/ | /blog/old-post/ | 200 | No change |
| /removed-page/ | /services/ | 301 | Content merged |
Every URL must have a destination. No URL should return a 404 after migration.
Redirect implementation:
- Code all 301 redirects
- Test redirects in staging environment
- Verify redirect chains (A → B → C) are minimised
- Ensure redirects work for all URL variations (trailing slash, www/non-www)
Phase 2 — Pre-Launch Testing (1–2 Weeks Before)
Staging environment checks:
- All redirects tested and working
- No redirect chains or loops
- All pages render correctly
- Metadata (title, description) correct on all pages
- Structured data valid on all pages
- Internal links updated to new URLs (not relying on redirects for internal navigation)
- XML sitemap updated with new URLs
- Robots.txt correct for new site
- Canonical tags pointing to correct URLs
- No noindex tags on pages that should be indexed
- Core Web Vitals acceptable on new site
- Mobile experience tested
Phase 3 — Launch Day
Execute in this order:
- Deploy new site
- Activate all 301 redirects
- Submit new XML sitemap to Search Console
- Add new property in Search Console (if domain changed)
- Use URL Inspection to request indexing of key pages
- Monitor for 404 errors in real-time
- Test critical pages and redirects manually
Phase 4 — Post-Migration Monitoring (1–12 Weeks After)
Week 1:
- Monitor Search Console for crawl errors daily
- Check for 404 spikes
- Verify Google is crawling the new URLs
- Fix any missed redirects
Weeks 2–4:
- Track keyword ranking changes
- Monitor organic traffic trends
- Compare traffic to pre-migration baseline
- Address any indexing issues
Months 2–3:
- Rankings should begin stabilising
- Traffic should approach pre-migration levels
- Continue monitoring for edge cases
- Update backlinks where possible (contact linking sites to update URLs)
Common Migration Mistakes
Missing redirects. Every old URL must redirect. Missing even a few high-traffic pages causes significant traffic loss.
Redirect chains. A → B → C → D wastes crawl budget and dilutes link equity. Redirect directly from old to final URL.
Internal links pointing to old URLs. Update internal links to point to new URLs directly — do not rely on redirects for internal navigation.
No baseline data. Without pre-migration traffic and ranking data, you cannot assess migration impact.
Changing URLs unnecessarily. If a URL does not need to change, keep it the same. Every URL change is a risk.
Removing the old redirects too soon. Keep 301 redirects active permanently (or at minimum 12 months).
Not updating the sitemap. Submit a new XML sitemap with the new URLs immediately after migration.
Recovery From a Bad Migration
If traffic drops significantly after migration:
- Audit redirects — check for missing, broken, or chained redirects
- Check Search Console — look for crawl errors, index coverage drops
- Verify canonical tags — ensure they point to the correct new URLs
- Review noindex tags — check that no pages are accidentally noindexed
- Check robots.txt — ensure Googlebot is not blocked
- Compare content — verify content parity between old and new versions
- Monitor and wait — some fluctuation is normal; allow 4–8 weeks before escalating
Key Takeaways
- Site migrations are the highest-risk SEO events — plan meticulously.
- Every old URL must redirect to its new equivalent via 301 redirect.
- Capture baseline data before migration to measure impact.
- Test everything in staging before going live.
- Expect 3–6 months of fluctuation; sustained drops beyond that indicate problems.
Quick Migration Checklist
- Pre-migration baseline captured (traffic, rankings, backlinks)
- Complete URL mapping document created (old → new)
- All 301 redirects coded and tested in staging
- No redirect chains or loops
- Internal links updated to new URLs
- XML sitemap updated with new URLs
- Robots.txt verified for new site
- Canonical tags correct on all pages
- Structured data validated on new pages
- Mobile experience tested
- New Search Console property added (if domain changed)
- Post-launch monitoring active (crawl errors, traffic, rankings)
- Redirects kept active permanently
Tools & Resources (Coming Soon)
- Migration Redirect Mapper (Coming soon)
- Migration Audit Checklist (Coming soon)
- Post-Migration Monitor (Coming soon)
Related SEO Documentation
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