A heritage fashion brand migrated without losing a single ranking.

The challenge

The client was a heritage UK fashion brand with a decades-long history and a substantial organic search presence built up over years of careful work. They needed to migrate their Shopify Plus store to a new theme — a full redesign with a restructured URL architecture, consolidated product taxonomy, and a new navigation model.

The risks were significant. The site had over 4,000 indexed pages, ranking across thousands of branded and non-branded keywords, including a number of highly competitive category terms that represented a material share of revenue. A standard theme swap done without proper migration engineering would have been catastrophic.

Our approach

We led the migration end-to-end, from pre-migration audit through to post-launch monitoring. The project ran across four months: one month of preparation, one month of build, two weeks of staged rollout, and ongoing monitoring through the stabilisation period.

Pre-migration audit. Before a single line of code was changed, we audited the existing site comprehensively — crawling all pages, documenting every URL pattern, mapping internal linking structure, recording structured data implementation, and establishing performance baselines across Core Web Vitals. We identified 14 pages carrying disproportionate ranking value that required special handling.

URL architecture design. The new site structure consolidated several legacy category paths that had accumulated over years of ad-hoc expansion. We designed the new architecture to preserve the topical signals of the old structure while cleaning up the duplication, then built a complete redirect map: every old URL mapped to its new destination.

Build oversight. We worked directly with the development team during the theme build, reviewing template code for SEO-critical elements at each stage — title tags, heading structure, canonical implementation, pagination, faceted navigation handling, product schema, breadcrumb schema. This caught seven issues before they went anywhere near production.

Staged rollout. Rather than a big-bang launch, we pushed the migration in three stages: new templates live on lower-priority pages first, then mid-tier, then the high-value category and landing pages. This gave us a window to catch any unexpected crawling behaviour before the most important pages were affected.

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The work

The most technically complex part of the migration was the faceted navigation. The old site had allowed search engines to crawl and index facet combinations, creating thousands of near-duplicate pages with thin content. The new theme gave us the opportunity to fix this properly — implementing crawl controls that allowed indexing of valuable filtered pages while blocking the combinatorial explosion of worthless variations.

We also rebuilt the product schema implementation from scratch. The old theme had partial structured data — some products had it, most didn't, and what existed was inconsistently formatted. The new implementation was complete, validated, and consistent across all product types.

Post-launch monitoring ran for six weeks. We watched crawl logs daily, tracked ranking movements on the top 200 terms weekly, and reviewed Search Console data for any indexation anomalies. Three redirect chain issues surfaced in week one — caught and fixed within 24 hours.

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The outcome

Zero ranking loss at migration. In the quarter following, organic traffic grew 18% — partly attributable to the improved page experience signals from the new theme, partly to the structured data improvements, and partly to the faceted navigation cleanup reducing crawl waste and improving indexation of genuinely valuable pages.

"We'd done a migration before without this level of support and it cost us six months of recovery work. This time we came out of launch with nothing to fix. That's not luck — it's preparation."

The structured data work subsequently fed into the client's AI Search programme, where entity clarity on product pages became a relevant signal for product-discovery queries.

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Related disciplines

This engagement draws on technical SEO, migration engineering, Shopify Plus development, and structured data implementation. It demonstrates the Build practice working in close coordination with the SEO practice — the kind of engagement where the two are inseparable.