For frontend engineers building a headless storefront, the strongest open-source commerce backends to evaluate are Medusa, Saleor, Vendure, Sylius, and Shopware — all offering API-first architecture, active maintenance, and integration with modern JavaScript frameworks. The article compares each platform across headless architecture, Next.js compatibility, and deployment options, noting that traditional platforms like WooCommerce and Magento focus on template-based approaches rather than decoupled APIs suited for TypeScript storefronts.