How to Handle SEO During a Website Migration

TL;DR

Website migrations are among the highest-risk SEO activities. Changing domains, platforms, URL structures, or site architecture can cause significant traffic loss if mishandled. Success requires: comprehensive redirect mapping (every old URL to its new equivalent), pre-migration audits and benchmarking, staged rollouts when possible, immediate post-launch monitoring, and documented rollback plans. Most migration traffic losses are permanent because issues aren’t caught quickly enough. The goal isn’t zero traffic loss (unlikely) but minimizing loss and recovering quickly.

Do This Today (Pre-Migration Checklist)

Crawl current site completely: Export all URLs, page titles, traffic data, backlinks. This is your baseline and redirect mapping source.

Identify high-value pages: Which pages drive 80% of traffic? These need perfect redirects and priority monitoring.

Document current rankings: Track rankings for top 50-100 keywords. You need pre-migration benchmarks to detect problems.

Migration Types and Risk Levels

Migration Type	Risk Level	Key Concerns
<strong>HTTP to HTTPS</strong>	Low	Redirect all HTTP to HTTPS, update internal links, update GSC property
<strong>Domain change</strong>	High	Full redirect mapping, brand signal changes, backlink value transfer
<strong>Platform change</strong> (same URLs)	Medium	Template changes, speed changes, technical implementation
<strong>Platform change</strong> (new URLs)	High	Redirect mapping + platform risks combined
<strong>Site structure change</strong>	Medium-High	Category changes, URL path changes, internal linking changes
<strong>Site consolidation</strong> (merging sites)	Very High	Multiple domains, content decisions, authority consolidation
<strong>International expansion</strong>	High	Hreflang, domain strategy, content localization

International/Hreflang Migration Considerations

When migrating sites with hreflang:

Scenario	Complexity	Key Steps
<strong>Same languages, new URLs</strong>	Medium	Update hreflang to point to new URLs across all language versions
<strong>Adding new languages</strong>	Medium	Implement hreflang on new + existing pages simultaneously
<strong>Changing domain strategy</strong> (subfolders to ccTLDs)	Very High	Full redirect mapping per language, hreflang update, GSC properties per domain
<strong>Consolidating international sites</strong>	Very High	Choose canonical language strategy, redirect deprecated versions

Hreflang migration checklist:

Map all language/region versions: Create matrix of old URL → new URL for each language
Update hreflang tags simultaneously: All language versions must update together
Redirect old URLs per language: /de/page/ → new-de-location/page/
Verify bidirectional hreflang: Each page must reference all alternates, including itself
Test with hreflang testing tools: Validate no orphan tags or conflicts
Monitor per-language GSC properties: Track each language version separately

Common hreflang migration mistakes:

Updating one language but not others (broken bidirectional)
Forgetting x-default tag
Redirect chains within language versions
Mismatched language codes (en-GB vs en-UK)

GSC Property Transition

For domain changes:

Step	Timing	Action
1. Verify new property	Pre-launch	Add and verify new domain in GSC
2. Keep old property	Ongoing	Don't delete old property, you need historical data
3. Submit change of address	Launch day	Settings → Change of address (domain moves only)
4. Submit new sitemap	Launch day	Submit sitemap to new property
5. Monitor both properties	Post-launch	Old property shows legacy data, new property shows current
6. Request indexing	Launch day	URL Inspection on key pages in new property

Change of Address tool requirements:

Available for domain-level changes (example.com → newexample.com)
Old site must still be accessible with redirects in place
Both properties must be verified
301 redirects must be implemented
Takes 6-12 months for full processing

For non-domain migrations (same domain, new structure):

No Change of Address tool needed
Same GSC property continues
Submit new sitemap with new URLs
Use URL Inspection to verify new URL structure
Monitor indexing of new URLs vs old URLs

Multiple GSC properties (international):

Domain Strategy	GSC Properties Needed
Subdirectories (/en/, /de/)	One property for main domain
Subdomains (en.example.com)	One property per subdomain OR domain-level property
ccTLDs (example.de, example.fr)	One property per ccTLD

The Conversation

Nadia, CMO at a mid-sized e-commerce company, planning migration from legacy platform to Shopify, 15,000 product pages, current platform has custom URLs that won’t match Shopify’s structure, leadership wants migration done in 6 weeks, concerned about SEO impact, intermediate SEO knowledge: We’re migrating from our legacy e-commerce platform to Shopify. We have 15,000 products and about 200 category pages. Our current URLs are structured completely differently than Shopify’s default structure. Leadership wants this done in 6 weeks. I’m terrified we’re going to destroy our organic traffic. How do we do this safely?

SDC SEO Brain: Your concern is justified. Platform migrations with URL structure changes are high-risk. Let me be direct: six weeks is aggressive for 15,000 products with URL changes. It’s possible but leaves little room for error. First question: how much of your traffic comes from organic search, and what would a 30-50% drop mean for the business?

Nadia: About 40% of our revenue comes from organic. A 50% drop would be catastrophic, potentially millions in lost revenue.

SDC SEO Brain: Then leadership needs to understand the risk. A rushed migration increases probability of significant traffic loss. That said, let’s plan for success. What are the URL structure differences?

Nadia: Current site: /products/blue-cotton-dress-12345
Shopify default: /products/blue-cotton-dress (no ID) plus Shopify forces /collections/ for categories.

SDC SEO Brain: The product URL change is manageable if you create proper redirects. Shopify’s forced structure is a constraint you can’t avoid. Let’s build your migration plan.

Phase 1: Pre-Migration (Weeks 1-2)

Complete crawl of current site:

Every URL (products, categories, blog, informational pages)
Current page titles and meta descriptions
Internal link structure
Traffic per URL (from GA/GSC)
Backlinks per URL (from Ahrefs/Semrush)

Nadia: What tool should I use for crawling?

SDC SEO Brain: Screaming Frog is standard. For 15,000 pages, you’ll need the paid version (free limited to 500 URLs). Export everything to spreadsheet. This becomes your redirect mapping foundation.

Redirect mapping preparation:
Create a spreadsheet with columns:

Old URL
New URL
Page traffic (prioritization)
Backlinks (prioritization)
Redirect type (301)
Status (pending, verified, live)

For each old URL, determine what it maps to. Most will be straightforward (/products/old-name → /products/new-name). Some may require decisions (discontinued products, merged categories).

Nadia: What about products that don’t exist anymore? We have some discontinued items.

SDC SEO Brain: Options for discontinued products:

If the product page has backlinks or traffic: Redirect to the most relevant alternative product or category page. Don’t lose that link equity.

If no backlinks or traffic: Redirect to parent category, or let it 404. Low-value pages don’t need individual treatment.

If you might restock: Keep the URL and show “out of stock” with related products. Don’t redirect URLs you might need again.

Nadia: How do we handle the actual redirect implementation on Shopify?

SDC SEO Brain: Shopify has a built-in URL redirect feature (Settings → Navigation → URL Redirects). For bulk uploads, you can import CSV files. For 15,000 redirects, you’ll need the CSV method. Test the import process with a small batch first.

Phase 2: Staging and Testing (Weeks 3-4)

Set up Shopify on a staging environment (password-protected so Google can’t index it). Then:

Verify redirects work:

Test a sample of redirects manually
Use Screaming Frog to crawl the redirect mapping
Check for redirect chains (old → intermediate → new) and fix them
Verify no redirect loops exist

Nadia: What’s a redirect chain and why does it matter?

SDC SEO Brain: A redirect chain is when URL A redirects to URL B, which redirects to URL C. Each hop loses some link equity and adds latency. Maximum acceptable: 2 hops. Ideal: 1 hop (direct old to new). If you have existing redirects from previous changes, you might accidentally create chains. Audit for these.

Template verification:

Do new page templates have all SEO elements? (title tags, meta descriptions, canonical tags, schema markup)
Are heading structures correct?
Do images have alt text fields?
Is the XML sitemap generating correctly?
Are robots.txt and noindex tags correct?

Speed testing:

Compare new site speed to old site
Shopify can be slower or faster depending on theme
If new site is significantly slower, fix before migration

Nadia: Should we test with real users?

SDC SEO Brain: Yes, if possible. User testing catches navigation issues, broken features, and UX problems that affect SEO indirectly. But keep the testing environment blocked from search engines.

Phase 3: Launch Preparation (Week 5)

Prepare GSC:

Verify the new domain (if changing domains) or prepare the existing property
Have new sitemap ready to submit immediately after launch

Prepare monitoring:

Set up rank tracking for top keywords
Prepare GSC monitoring dashboard
Set up uptime monitoring
Prepare traffic comparison views in analytics

Communicate timeline:

Inform relevant teams (customer service, marketing, leadership)
Plan for reduced organic traffic during transition
Have contingency budget for paid ads if organic drops significantly

Finalize rollback plan:

Document how to revert if disaster strikes
Ensure old site can be quickly restored
Define decision criteria for rollback (what level of problem triggers rollback)

Nadia: What would trigger a rollback decision?

SDC SEO Brain: Have clear criteria decided in advance:

90%+ of redirects not working → immediate rollback
Major functionality broken (checkout, search) → immediate rollback
50%+ traffic drop within 48 hours with no technical explanation → consider rollback
Google deindexing pages rapidly → investigate, consider rollback

Rollback is disruptive, so the threshold should be severe problems, not normal migration fluctuations.

Phase 4: Launch (Week 6)

Launch timing:

Launch Tuesday-Wednesday (not Friday, not before holidays)
Launch in the morning (time to fix issues same day)
Have all technical resources available

Immediate post-launch:

Submit new sitemap to GSC
Use GSC URL Inspection on key pages to request crawling
Verify redirects are working (sample testing)
Verify site is accessible (no accidental noindex, robots.txt blocks)
Monitor uptime actively

Nadia: How quickly should we see issues if something’s wrong?

SDC SEO Brain: Technical issues (site down, redirects broken, accidental noindex) surface within hours. Traffic impact takes longer to assess, typically a few days minimum. Don’t panic at day 1 fluctuations. Do panic at site errors, broken redirects, or indexing blocks.

Phase 5: Post-Migration Monitoring (Weeks 7-12)

First week:

Daily monitoring of traffic, rankings, crawl errors
Fix any broken redirects found
Address any GSC errors immediately

First month:

Weekly detailed analysis
Compare to pre-migration benchmarks
Monitor indexing progress of new URLs
Watch for traffic patterns stabilizing

First quarter:

Monthly comprehensive review
Rankings should stabilize or improve
If still declining after 2 months, investigate deeper issues

Nadia: What if traffic drops and doesn’t recover?

SDC SEO Brain: Some migration traffic loss is normal (5-15% temporarily). If you’re seeing larger drops:

Check redirect implementation: Are old URLs actually redirecting? 404s instead of 301s are common mistakes.

Check indexing: Are new URLs being indexed? Are old URLs dropping from index?

Check canonical tags: Are canonicals pointing to correct URLs? Incorrect canonicals can deindex pages.

Check for technical issues: Speed degradation, mobile issues, blocked resources.

If everything looks correct but traffic doesn’t recover within 3 months, you may have content quality issues or competitive displacement unrelated to migration.

FAQ

Q: How much traffic loss is normal during migration?
A: Well-executed migrations typically see 5-15% temporary loss that recovers within 1-2 months. Poorly executed migrations can lose 30-80% and never fully recover. Zero loss is possible but rare.

Q: How long do redirects need to stay in place?
A: Minimum 1 year, ideally permanently. Redirects transfer link equity. Removing them too soon loses that value. Shopify doesn’t charge extra for redirects, so leave them forever.

Q: Should we change URLs to be more SEO-friendly during migration?
A: Only if current URLs are significantly problematic. Every URL change requires a redirect and carries risk. Don’t change URLs just to make them “better” unless current URLs are truly bad (like /page?id=4829).

Q: Can we migrate in phases (some pages first, then others)?
A: Yes, and this is often safer for large sites. Migrate a section, verify success, then continue. Phased migration adds complexity but reduces total risk.

Q: What if we’re also redesigning during migration?
A: This multiplies risk. If possible, separate migration (technical, URLs) from redesign (templates, content). Combining makes it impossible to diagnose which change caused problems.

Summary

Website migrations are high-risk SEO events. Traffic loss is common, often permanent if issues aren’t caught quickly.

Pre-migration preparation is critical:

Complete site crawl and URL inventory
Redirect mapping for every URL
Benchmark current traffic and rankings
Identify high-priority pages

Redirect mapping prevents traffic loss:

Every old URL needs a 301 to new equivalent
No redirect chains (old → new directly)
Test redirects before launch
Monitor for 404s after launch

Staged testing catches issues:

Staging environment for verification
Template SEO elements verification
Speed comparison
Redirect testing

Post-migration monitoring is essential:

Daily monitoring first week
Weekly analysis first month
Quarterly review for recovery
Quick response to technical issues

Have a rollback plan. Document criteria for rollback and ensure you can restore the old site quickly if needed.

Timeline matters. Rushed migrations have higher failure rates. Push back on unrealistic timelines when SEO traffic is significant to the business.

Sources

Google Search Central: Site moves – https://developers.google.com/search/docs/crawling-indexing/site-move-with-url-changes
Google Search Central: 301 redirects – https://developers.google.com/search/docs/crawling-indexing/301-redirects
Shopify: URL redirects – https://help.shopify.com/en/manual/online-store/menus-and-links/url-redirect

SDC SEO