Replatforming an ecommerce store is one of the highest-risk projects in digital retail. Done well, it's invisible to customers and transformative for the business. Done badly, it's the reason organic traffic falls off a cliff the week after launch — and it takes months to recover, if it recovers at all.
This checklist walks through an SEO-safe ecommerce migration for UK retailers: when to migrate, how to plan it, the redirect mapping that protects your rankings, and the post-launch monitoring that catches problems early. If migration is part of a bigger growth plan, our ecommerce growth work covers the strategy side; this article is the practical execution guide.
First: should you actually migrate?
Migration is expensive, disruptive, and risky. Before committing, be honest about the trigger. Good reasons: the platform can't handle your traffic or order volume, checkout conversion is structurally limited, integrations you need don't exist, or total cost of ownership has become absurd. Bad reasons: a competitor's site looks nicer, someone at a conference raved about a platform, or you're bored.
If the trigger is performance or conversion rather than capability, a rebuild on your current platform or targeted maintenance and optimisation may deliver 80% of the benefit at 20% of the risk. Migrate when the platform is the constraint, not when the design is tired.
Phase 1: Audit everything (4–6 weeks before build)
Crawl the current site completely
Run a full crawl and export every URL: products, categories, blog posts, landing pages, policy pages, everything. For each URL, record its organic traffic, revenue attributed, backlinks, and rankings. This inventory is the foundation of the whole migration — you cannot protect what you haven't mapped.
Pay special attention to:
- Top 20% of pages by revenue. These get individual attention in the redirect map. A 301 for your best-selling category page is not a detail — it's the business.
- Pages with backlinks. Use a backlink tool to find every URL with external links pointing at it. Losing link equity through bad redirects is the classic migration injury.
- Long-tail product pages. Individually small, collectively significant. They need redirect rules, not individual mapping — which means your URL structure planning has to be right.
- Non-obvious traffic pages. The blog post from 2019 that ranks for a buying keyword, the delivery information page that captures "brand + delivery" searches. Crawl data plus analytics will surface them.
Benchmark current performance
Record baselines for organic traffic, keyword rankings (your top 200), conversion rate, average order value, site speed, and indexed page count. You'll compare against these weekly after launch. Without baselines, you won't know whether a dip is migration damage or normal fluctuation.
Document the current SEO setup
Title tag patterns, meta description templates, heading structures, schema markup, canonical tags, hreflang (if you sell internationally), XML sitemaps, robots.txt rules. Every one of these needs a deliberate decision on the new platform: keep, improve, or replace. "We'll sort SEO after launch" is how migrations fail.
Phase 2: Plan the new structure (during build)
Design URLs before content
Decide the new URL structure early and map old to new in a spreadsheet with three columns: old URL, new URL, redirect type. Rules of thumb:
- Keep URLs as close to the old structure as possible. Change platform, not architecture, unless the architecture was broken.
- Use pattern-based redirects for product and category pages (e.g. /shop/widgets/* → /products/*) and individual 301s for high-value pages.
- Every old URL must resolve to something sensible: the equivalent new page, the closest category, or — only as a last resort — the homepage. Never let old URLs 404 if they had traffic or links.
- Plan for discontinued products: redirect to the closest live alternative, not a dead page. A 404 on a page with backlinks wastes the links.
Protect the technical SEO foundations
- Title tags and meta descriptions: migrate them, don't regenerate blindly. If the new platform auto-generates them, review the templates against your top pages.
- Schema markup: product, review, breadcrumb, and organisation schema should be present and valid on day one. Test with Google's rich results tool before launch.
- Canonical tags: faceted navigation and filtered category pages are canonical-tag minefields. Decide the strategy now — usually canonicalise filtered views to the main category.
- Internal linking: the new theme's navigation, footer, and cross-sell blocks redistribute link equity. Make sure important categories are reachable within a few clicks from the homepage.
- Image SEO: migrate alt text, keep filenames sensible, and don't serve 4MB images because the new theme "handles it".
Handle the content migration honestly
Thin, duplicated, or outdated content is a migration opportunity, not just a chore. But be careful: deleting pages that rank, even thin ones, costs traffic. The rule is consolidate, don't just delete — merge thin pages into stronger ones and redirect the old URLs. Our guide to URL structure for SEO covers the principles behind these decisions.
Phase 3: Pre-launch testing (1–2 weeks before go-live)
- Test every redirect in a staging environment. Crawl the old URL list against staging and confirm each returns the correct 301 to the correct destination. One broken redirect rule can 404 thousands of product pages.
- Crawl the staging site for 404s, redirect chains, duplicate titles, and missing canonicals. Fix them before launch, not after.
- Test checkout end to end with real payments in test mode, on mobile. Migration is not the time to discover the new checkout doesn't take Apple Pay.
- Verify tracking. Analytics, ad pixels, affiliate tracking, consent mode for UK GDPR — all firing, all correct.
- Prepare the XML sitemaps for the new structure and have the robots.txt ready. Don't let the staging robots.txt (usually blocking everything) go live by accident — this happens more often than anyone admits.
- Plan the launch window. Go live at your lowest-traffic time (often Tuesday–Thursday early morning), never on a Friday, never before a peak period. Black Friday migrations are a horror story genre of their own — see our Black Friday checklist for why November is sacred.
Phase 4: Launch day and the weeks after
Launch day
- Deploy redirects and go live. Immediately crawl the old URL list in production and confirm the 301s work.
- Submit the new XML sitemap in Google Search Console. Use the change-of-address tool only if the domain itself changed.
- Monitor real-time analytics, checkout completion, and server errors for the first 24 hours. Have the rollback plan ready — knowing you can revert is what lets you launch calmly.
Weeks 1–4: monitor like a hawk
- Daily: Search Console coverage errors, crawl stats, and 404s from the server logs. Fix redirect gaps the same day they appear.
- Weekly: compare organic traffic, rankings for your top 200 keywords, conversion rate, and revenue against pre-launch baselines. Expect some fluctuation for 2–4 weeks; investigate anything worse than a 10–15% dip.
- Watch the money pages first. If your top category pages hold their rankings, the migration is probably fine. If they drop, it's urgent.
- Keep the old redirect map live for at least 12 months. Google needs time to process the changes, and old backlinks keep sending traffic indefinitely.
Common post-migration problems
| Symptom | Likely cause | Fix |
|---|---|---|
| Traffic drops 30%+ in week one | Missing or wrong redirects; staging robots.txt went live | Audit redirects immediately; check robots.txt and indexing |
| Category pages de-indexed | Accidental noindex; canonical tags pointing wrong | Crawl and fix tags; request re-indexing |
| Rankings fine, conversions down | Checkout friction; slower pages; broken trust signals | UX audit of the new checkout; speed test |
| Old URLs still ranking months later | Redirects not implemented or returning wrong codes | Verify 301s (not 302s) in production |
The honest bottom line
An SEO-safe migration is 80% planning and 20% execution. The redirect map, the baselines, and the content decisions made weeks before launch determine the outcome far more than launch-day heroics. Take the time, test everything twice, and monitor ruthlessly afterwards.
If you're weighing a move and want an honest assessment of whether migration is even the right call — or help executing one safely — talk to us.
FAQs
How long does an ecommerce platform migration take?
For a typical UK SME store, expect 8–16 weeks from audit to post-launch monitoring: 2–4 weeks auditing and planning, 4–8 weeks building, 1–2 weeks testing, and 4 weeks of close monitoring. Larger catalogues and complex integrations take longer.
Will migrating platforms hurt my SEO?
It can, but it doesn't have to. Most migration traffic losses come from missing redirects, accidental noindex tags, or changed URL structures without mapping. A complete redirect map, pre-launch testing, and post-launch monitoring keep the risk low.
What is redirect mapping?
Redirect mapping is the spreadsheet (and implementation) that connects every old URL to its new equivalent via 301 redirects. High-value pages get individual mappings; long-tail pages get pattern-based rules. Every old URL with traffic or backlinks must resolve somewhere sensible.
When is the best time to migrate an ecommerce store?
Your quietest trading period — for most UK retailers that's mid-January to March. Never migrate before Black Friday, Christmas, or any planned peak. Launch mid-week in the early morning, when traffic is lowest and your team is available.
Should I change my URL structure during migration?
Only if the current structure is genuinely broken. Changing platform and architecture simultaneously doubles the risk. If you must change both, the redirect map becomes even more critical, and you should allow extra monitoring time.
