Vue Storefront - Open Source PWA for any eCommerce
OpenCart - A free shopping cart system. OpenCart is an open source PHP-based online e-commerce solution.s
Square Online Checkout - Create easy pay links for whatever you're selling and start accepting payments everywhere online.
PrestaShop - Create your online store with PrestaShop's free shopping cart software. Build an ecommerce website for free and start selling online with hundreds of powerful features.
Shopify - Shopify is a powerful ecommerce platform that includes everything you need to create an online store and sell online. Try it free for 14 days.
WooCommerce - A freely available eCommerce plugin that enables shop facilities on your WordPress website. Functionality enabling extensions & beautiful themes available.