§ 01 The inheritance
What you bring from the legacy platform
A migrating ecommerce brand brings five things from the legacy platform. Accumulated URL equity (Google rank, backlinks, domain authority). Product catalog content (PDP copy, images, metadata, variants). Schema markup (whatever the legacy platform was emitting — often partial). Customer data and order history (handled separately by the migration tools, not an SEO concern). And the existing AI-engine citation graph (if the legacy site was being cited at all, those citations have to survive the URL change).
Each carries its own migration risk. URL equity is preserved by redirect mapping (next section). Product catalog content needs platform-format conversion plus quality review. Schema markup re-emits from the new Shopify theme but needs validation against the rich-results-test suite to verify the new output matches or exceeds the legacy. Customer and order data flows through Shopify's native or app-based migration tools. AI-engine citation graph is the hardest — citations referencing the old URLs need redirects in place; brand-name citations survive automatically but URL-specific citations do not.
§ 02 Redirect mapping
Redirect mapping is the migration's single most important task
The redirect map is what preserves 5-10 years of URL equity through the migration. Every old URL — product pages, collection/category pages, blog posts, info pages, sitemap entries — needs a 301 to the new Shopify URL. The map is built from the legacy platform's URL inventory (often exported from the platform's own admin or a crawl), mapped product-by-product to the Shopify URL structure, applied via Shopify's URL Redirects (manual or bulk CSV import), and validated by crawling the legacy URL set post-launch to verify every URL returns a 301 to the correct new destination.
Shopify's URL structure is opinionated: products live under /products/[handle], collections under /collections/[handle], blog posts under /blogs/[blog-handle]/[post-handle], pages under /pages/[handle]. Legacy platforms have different URL conventions — BigCommerce uses /products/[name]/, WooCommerce uses /product/[slug]/ or /shop/[slug]/, Magento uses /catalog/product/view/id/[id]/ or category-prefixed paths. The handle conversion is mechanical; the mapping work is matching each legacy URL to its new Shopify counterpart and handling edge cases (consolidated SKUs, retired products that should redirect to a category, blog posts that no longer apply).
§ 03 PDP copy port
PDP copy port — what to keep, rewrite, and replace
The PDP copy port is the migration's content-quality opportunity. Three categories of copy exist on the legacy platform. Brand-original copy (the merchant's own writing — keep, port as-is, verify the formatting renders correctly in Shopify). Manufacturer-default copy (text supplied by the product manufacturer, often used as a placeholder — rewrite during migration, because Shopify warns explicitly against duplicating manufacturer text). Generic or templated copy (LLM-generated, agency-templated, or copy-paste across products — rewrite for differentiation, because thin and duplicate copy underperforms in AI extraction).
The migration is the rare opportunity to address PDP copy quality at scale without disrupting an active site. Brands with 100-500 SKUs typically have at least 20% of PDPs running on manufacturer-default or templated copy2, and the migration timeline (4-12 weeks for most brands) accommodates the rewrite work that would be hard to schedule on an in-flight site. The install sequences the rewrite during migration: the redirect map is built first, the copy port happens during the rewrite window, the new Shopify PDPs launch with cleaner content than the legacy site had.
§ 04 Schema
Schema re-emission from Shopify themes
Shopify themes emit Product, Offer, BreadcrumbList, and Organization schema by default. The exact schema emitted depends on the theme — Dawn (Shopify's reference theme) emits a comprehensive set; some third-party themes emit partial or non-standard schema. The migration is the chance to standardize on a theme with strong schema emission, add custom JSON-LD via theme.liquid where the theme falls short, and validate the new schema layer against the Rich Results Test before launch.
Shopify's SEO overview1 documents the auto-emitted schema, auto-canonicals, and auto-sitemap features. The migration validation: every PDP in Rich Results Test returns valid Product schema with the rich-results-eligible fields populated (name, image, description, sku, brand, offers with price and availability). Every collection in Rich Results Test returns valid BreadcrumbList. Every blog post returns valid Article schema. Where the theme is insufficient, the install adds custom JSON-LD via theme.liquid injection — additionalProperty blocks for niche-specific metafields, OfferShippingDetails for furniture and food, hasMerchantReturnPolicy for the broader catalog.
§ 05 Platform notes
Three legacy platforms account for most Shopify migrations. BigCommerce shares many SEO defaults with Shopify but uses different URL conventions and a different variant model — the migration is mostly URL re-mapping and metafield consolidation. WooCommerce migrations are higher-friction because WordPress hosting variability means the legacy URL structure is less predictable and the schema emission depends on which SEO plugin the store was running. Magento migrations are the most complex because Magento's catalog model includes attributes, configurable products, and bundled products that don't map 1:1 to Shopify's variant model.
BigCommerce → Shopify: URL convention shift (/products/[name]/ → /products/[handle]/), variant model is similar enough to port mechanically, the BigCommerce-emitted schema typically validates clean in Shopify after migration. Estimated migration timeline: 4-8 weeks for catalogs under 1,000 SKUs.
WooCommerce → Shopify: URL convention varies by WordPress permalink setup (could be /product/[slug]/, /shop/[slug]/, or any custom permalink the merchant set), the variant model maps to Shopify cleanly but attribute handling needs review (WooCommerce's flexible attributes can become metafields rather than variants on Shopify), schema depends entirely on which WordPress SEO plugin was emitting it. Estimated migration timeline: 6-12 weeks for catalogs under 1,000 SKUs.
Magento → Shopify: the highest-complexity migration. Magento's URL structure (often /catalog/category/view/id/[id]/ for categories) needs explicit re-mapping, configurable products with multiple attribute axes map to Shopify variants but need consolidation under the 2,048-variant ceiling, bundled products typically need to be re-architected as separate products with linked-products metafields or as configurator UIs. Estimated migration timeline: 8-16 weeks for catalogs under 1,000 SKUs.
§ 06 The curve
The 90-day post-migration recovery curve
Migrations cause a temporary SEO dip. Google re-indexes the new domain or new URL structure over 4-12 weeks, AI engines pick up the new Catalog feed on a similar cadence, and the redirect graph takes time to flow link equity to the new URLs. The realistic curve: weeks 1-4 show indexed coverage drop as Google retires old URLs; weeks 5-8 show coverage rebuild as new URLs index; weeks 9-12 show traffic and citation recover to baseline (and often exceed baseline if the migration also improved content quality and schema).
The install's post-launch verification cadence runs weekly for the first month, biweekly for the second month, monthly thereafter. Week 1 verifies redirect coverage (every legacy URL returns 301 to the right destination). Week 2 verifies sitemap submission and initial indexing3. Week 4 verifies AI-engine pickup (catalog visible to ChatGPT, Perplexity, Gemini, Copilot test queries). Weeks 5-12 verify traffic recovery against baseline and address any remaining redirect or content issues surfaced in the analytics. The Catalog optimization doc5 recommendations are layered in during weeks 5-12 once the structural migration is stable — the new platform is the chance to populate the seven AI-readable fields properly across the whole catalog.
