Ecwid by Lightspeed

Ecwid solves a problem the rest of this category tends to ignore: a business already has a website it is happy with, and now needs to sell something. Rather than requiring a move, it embeds a working store into the site that exists, and keeps one inventory behind however many places the products appear.

That embedding is the entire design. The catalogue, cart and checkout are hosted by Ecwid and rendered inside the host page, so the surrounding site keeps its design, its address and its content, and the store can be added to a second site or a social channel without duplicating the products.

The catch is that the store's appearance is constrained by being a component rather than the page, and the cheapest plan allows only a handful of products and no domain of its own. It does publish a standalone storefront on a domain the merchant owns from the second tier upward, so the embedded case is a choice rather than the only option — but that tier costs more than several complete platforms, which is the point at which keeping the existing site has to be worth paying for.