Safe SEO migration: replatform and rebrand

Q: What if I lost traffic and do not know why?

Semalt Migration Diagnostic runs 40+ tests against the new site and compares with baseline. Detects the 12 most common causes of post-migration traffic loss: broken canonical, invalid hreflang, lost schema, robots.txt blocking, broken redirects, thin content, missing meta tags, etc.

Q: Is it different for SPAs (React/Vue)?

Yes. Semalt handles SPAs with Chromium rendering in the crawler to validate Google can index content. Migrating from SSR to CSR without planning typically loses 40%+ of traffic — Semalt warns before.

Q: Can I migrate without freeze?

Not recommended. Production changes while preparing the new site generate impossible-to-reconcile divergence. A 1-2 week freeze is standard in professional migrations.

The 5 migration types and their SEO risk
Why 62% permanently lose traffic
Pre-migration: complete snapshot
301 redirect mapping (the critical part)
Launch day: live checklist
Post-launch: 90-day monitoring
Case: ecommerce that migrated Vtex → Shopify without losing traffic
Master 50-point checklist
FAQs

62%

Migrations that lose traffic

Points in master checklist

90d

Post-launch monitoring

100%

URLs with backlinks preserved

The 5 migration types and their SEO risk

Type	Example	SEO risk	Project duration
Platform change (replatform)	Vtex → Shopify, WordPress → Headless	High	2-4 months
Domain change	mybrand.co.uk → mybrand.com	Very high	3-6 weeks
Rebrand with new URLs	old-brand.com → new-brand.com	Very high	2-3 months
HTTPS + www / non-www	http://x.com → https://www.x.com	Medium	1-2 weeks
URL restructure	/products/x-123 → /shop/category/x	High	3-6 weeks

The most dangerous migration is the one combining several types

Changing platform + domain + URL structure at the same time triples risk. Google needs to reprocess the whole site and any error compounds. Rule: if you can split into 2-3 phases, do it — never migrate 3 dimensions on the same day.

Diagram: crawl, render, index, rank — the four stages a page must pass and what breaks at each — Four stages, four different failure modes. An audit is worth doing in this order — fixing rank signals on a page that is not indexed changes nothing.

Why 62% permanently lose traffic

The 5 things successful migrations do

Complete pre-migration snapshot (100% URLs)
1:1 301 redirect map (not batch)
Staging site with pre-launch crawl
Daily monitoring for first 30 days
Communication to Google Search Console

The 5 errors that ruin migrations

Batch redirects to the home (everything to /)
Not mapping URLs with backlinks
Redirect chains (301 → 301 → 200)
Forgetting hreflang and canonical
Migrating without updated sitemap

Pre-migration: complete snapshot

Semalt runs a complete crawl of the current site and captures:

Pre-migration snapshot (17 points)

All indexed URLs (via crawler + sitemap + Search Console)
Current position of top 500 keywords
Organic traffic per URL (Semalt Analytics + Search Console)
Inbound backlinks per destination URL
Structured schema on each URL
Current meta title and description
H1, H2 structure per template
Current canonical per URL
Declared hreflang alternatives
Robots directives (index/noindex, follow/nofollow)
Paginated URLs with rel="next"/"prev" (if applicable)
Existing redirects (important: do not break working chains)
Core Web Vitals baseline per template
Fullpage screenshots of top 50 URLs
Internal link structure (graph)
Anchor text distribution
Assets: images, videos, PDFs referenced

The snapshot is saved as baseline in Semalt and automatically compared against the new site post-launch.

301 redirect mapping (the critical part)

Redirect mapping is where most migrations die. Semalt Migration has 3 modes:

Auto 1:1

When URL structure is predictable (same slug, different base). Semalt generates 1:1 mapped CSV in seconds.

Semantic AI

When URL structure changes. Semalt compares old URL content vs new candidate URLs and suggests match with confidence score.

Assisted manual

For critical URLs (top 100 in traffic or with 10+ backlinks). Mandatory human approval before execution.

Golden rule of 301 redirects

Each old URL must redirect to the most semantically equivalent new URL. Never redirect everything to home — Google treats that as «soft 404» and discounts link juice. If no exact equivalent, redirect to the closest parent category.

Configuring redirects without chains

A redirect chain (URL A → URL B → URL C) loses 15% link juice per hop and confuses the crawler. Semalt detects existing chains and collapses to direct redirects:

/old-1 → /old-2 → /new becomes /old-1 → /new + /old-2 → /new
Applied automatically via the redirects file (nginx.conf, .htaccess, Vercel/Netlify config, or Cloudflare Worker)
Automatic curl -I verification: each old URL must return 301 directly to the final new URL with 200

Launch day: live checklist

T-24h

Freeze changes on old site

No dev commits changes to current site. Semalt runs final snapshot.

T-2h

Deploy staging with robots noindex

New site up on staging with robots.txt: Disallow / while QA verifies. Semalt crawls staging and validates.

T-0

DNS switch + robots allow

DNS change to new server. Robots.txt changes to allow crawl. Redirects active from minute 1.

T+30min

Verification with Semalt Live Monitor

Semalt curl-tests 500 critical URLs and validates: correct 301, no chains, new URL content matches expectation.

T+2h

Submit new sitemap

New sitemap sent to Search Console. Change of address filed. IndexNow ping to Bing and Yandex.

T+24h

First indexation report

Semalt verifies how many new URLs already crawled by Googlebot. Alerts on abnormal traffic drop.

Post-launch: 90-day monitoring

Normal timeline of a well-executed migration

Days 1-14: temporary 15-30% drop in organic traffic — normal, Google is reprocessing. Days 15-45: gradual recovery, stabilises at +/- 5% of baseline. Days 45-90: if the new site is better (faster, better schema), it typically RISES above baseline. If at 45 days still -20% or more, something is broken.

Daily Semalt Migration Monitor

Crawl status

How many new URLs indexed vs total expected. Target: 90% in 30 days.

Redirect health

Daily verification that all 301s keep responding correctly. Zero chains.

Traffic delta

Total organic traffic vs pre-migration baseline. Segmented by template and head keyword.

Position tracking

Top 500 keywords tracked 3x/day with Rank Tracker from residential IPs.

Backlink integrity

Inbound backlinks: verifies redirects preserve link juice. Alerts if a high-DA backlink points to a 404 URL.

Schema validation

Daily schema audit on migrated URLs. Detects if Product schema lost fields, if FAQ changed.

Case: ecommerce that migrated Vtex → Shopify without losing traffic

We migrated from Vtex to Shopify Plus in March 2026. Had 3,400 products, 47k monthly organic sessions and 6 years of SEO history. Without Semalt we would have lost months. With Semalt Migration the maximum drop was -12% on day 8, we recovered baseline on day 24 and by 60 days we were +18% above baseline.

CTO, home decor ecommerce

Day 8 (maximum temporary drop)-12%

Day 24 (baseline recovery)0%

Day 60 (post-migration)+18%

URLs correctly mapped 1:13,398 of 3,400

The 2 unmapped URLs were discontinued products without equivalent — redirected to parent category correctly.

Master 50-point checklist

Phase 1: Preparation (2-4 weeks before)

Execute complete Semalt Migration snapshot
Document all current indexed URLs
Capture position of top 500 keywords
Export inbound backlinks per destination URL
Document structured schema per template
Core Web Vitals baseline per template
Audit current canonical and hreflang
Freeze changes on production

Phase 2: Mapping (1-2 weeks before)

Generate 1:1 redirect map via Semalt Auto
Review high-traffic URLs manually
Review URLs with backlinks manually
Validate 0 redirect chains
Configure redirects in nginx / Apache / Cloudflare
Prepare new sitemap.xml
Prepare new robots.txt
Prepare new hreflang and canonical

Phase 3: Staging (1 week before)

Deploy new site on staging with robots noindex
Complete staging crawl with Semalt
Validate schema across all new templates
Verify Core Web Vitals equal or better
QA of forms, checkout, critical features
Test redirects from staging

Phase 4: Launch (D-day)

T-24h: freeze changes old site
T-2h: deploy new with robots noindex
T-0: DNS switch + robots allow crawl
T+30min: Semalt Live Monitor verification
T+1h: submit new sitemap Search Console
T+1h: Change of address if domain changes
T+2h: IndexNow ping Bing/Yandex
T+24h: first indexation report

Phase 5: Monitoring (90 days)

Daily: Crawl status via Semalt Migration Monitor
Daily: Redirect health check
Daily: Traffic delta vs baseline
Daily: Position tracking top 500 keywords
Weekly: Backlink integrity check
Weekly: Schema validation
Weekly: Stakeholder report
Day 30: formal review, adjustments if traffic >20% down
Day 60: content refresh review
Day 90: migration project closure

More in this series: Semalt Analytics: the SEO data GA4 hides, Semalt AutoSEO: optimisation that runs 24/7, Competitor analysis without leaving a trace.

FAQs

How long does a complete migration take?

Depends on type. A mid-sized ecommerce replatform (3,000 SKUs): 8-10 weeks total project (4 prep + 4 post-launch stabilisation). A simple domain change: 3-5 weeks.

Can I migrate without traffic loss?

Yes, it is possible. In 40% of Semalt-executed migrations, the maximum temporary drop was <15% and by day 45 the new site surpassed baseline. Requires discipline in redirect mapping.

What if I lost traffic and do not know why?