An open source shopping cart is an eCommerce platform that is available for free to anyone who would like to use it. There are no licensing fees or restrictions on who can use the software. This means that anyone can download the software, customize it to their own needs, and use it to build an online store. There are many different open source shopping carts available, each with its own unique set of features. Some of the most popular open source shopping carts include Magento, OpenCart, PrestaShop, and WooCommerce.