Where it gets stuck.
he clean version of a Magento-to-Shopify migration looks like a CSV export from Magento, a Shopify Matrixify import, and a few hundred 301 redirects. The real version involves four exports that don't match: products with custom attributes Magento allowed and Shopify doesn't model, customer accounts with hashed passwords Shopify cannot rehydrate, URL structures with .html suffixes Shopify rewrites, and category trees Shopify flattens into collections without preserving parent-child relationships.
Why it happens.
Magento and Shopify are different commerce primitives. Magento treats a catalog as a hierarchical tree with arbitrary depth and per-node attribute templates. Shopify treats it as a flat product table with collection-based grouping. The migration tools move the data but not the model — product rows transfer, but the configurable-product variant logic, the attribute groups, and the category-attribute inheritance Magento gave you for free have no Shopify equivalent. A standard migration moves the bytes and breaks the architecture.
The size of it.
A direct Magento-to-Shopify migration handled by a typical agency takes 4–8 weeks for a 5,000-SKU catalog and ships with 12–25% of products needing manual cleanup post-launch. We have seen brands lose 30–60% of organic traffic in the first 90 days after a migration that didn't preserve URL structure correctly. The work that actually matters in a Magento migration is not the data transfer — it is the slug-to-slug redirect map, the variant architecture redesign for Shopify's three-axis model, and the trade/B2B price list mapping. Get those three right and the migration ships cleanly; miss any one and the launch costs more than the build.
Filed from inside a working engagement. Edited only for client privacy — the numbers and the mechanisms are exact.