A replatform is not a theme swap. It is store migration: catalog, media, customers, orders where the APIs allow, a redirect map, checkout on the destination stack, and a freeze window so two shops do not sell the same SKU at once. Related catalog work includes euromoskitka and ecosteks.ru as commercial fronts — not as a trophy for every pair below.
The process is the same even when the engines differ: audit the source (PHP version, locked modules, dirty SKUs), decide what must survive, export, map URLs, rebuild payments and shipping for the target market, test on staging, cut over, hypercare. Inventory after go-live is ERP sync. Shopping feeds after the URL map is catalog SEO and merchant feeds. Destination platforms are the stack pages above, not a second copy of those briefs.
OpenCart or custom PHP to Shopify
OpenCart and one-off PHP shops are the usual English-market sources when hosting and checkout have become a second job. Shopify is the default destination for DTC: managed checkout, Stripe, apps. We export products and customers, rebuild collections, and 301 the old catalog. Customer passwords rarely survive; we plan a reset, not a surprise. 1C-Bitrix is not the target on this pair.
OpenCart or Magento 1 to WooCommerce
WooCommerce wins when WordPress content is the acquisition engine or you want code on PHP hosting you already run. Magento 1 and OpenCart catalogs can land here if the theme stays updateable and we do not import a plugin landfill. See WooCommerce.
Magento 1 to Adobe Commerce
A Magento 1 “upgrade” is a replatform, not a button in admin. Adobe Commerce (Magento 2) is the destination only when B2B companies, quotes, and multi-store complexity are real. Otherwise Shopify Plus or Woo is cheaper to own. I will refuse a status-symbol Magento 2 for a 200-SKU DTC brand.
1C-Bitrix is not the default destination
For US/EU teams I do not migrate onto 1C-Bitrix. Bitrix is a CIS/accounting contour — see 1C-Bitrix stores. If your source happens to be Bitrix and the destination is Shopify or Woo, that pair is in scope; the ledger work stays on 1C integration.
A contained replatform often lands in 6–12 weeks after the audit; dirty catalogs and ERP remaps add calendar time. We do not promise “weekend migration, keep every URL magically.”