Ecwid claims to be the “most popular store-builder app” on Facebook and to have 300,000 active monthly users.

Whether that’s true or not, the Southern Californian company did announce today that it has closed $5 million in its second round of funding. Ecwid said it will put its new funds toward its mobile- and social-commerce products, adding more partners to its global distribution network, increasing its sales and marketing teams, and working to integrate the online cart with merchants’ point-of-sale (POS) systems.

Ecwid’s shopping cart is a widget, and thus, online retailers into any existing website without too much effort. It offers a free starter plan for stores with less than ten products, with monthly fees kicking in beyond that. Not surprisingly, Ecwid shares founders with X-Cart, a PHP shopping cart.

“Ecwid is popular because it is a true sell-anywhere storefront with universal integration on any online platform. This is a reason it has had stellar growth and profitability with a first round funding of just $1.5 million,” said iTech Capital managing partner Gleb Davidyuk (whose company invested in this round) in an official statement.

“Ecwid’s market of small business merchants also is where the e-commerce growth of the next decade will be found. There are millions of sites built with WordPress, Wix, Squarespace, Weebly and Yola that now can embed a full-featured store in minutes. This is a great business opportunity, a great management team and much potential growth for our shareholders.”

While other e-commerce companies focus on making online selling as easy as possible for merchants by offering one-stop-shop solutions (Bigcommerce is a great example), Ecwid seems to be focused on creating a shopping cart tool that can integrate into existing Web presences without calling for any changes in the content management system. It also wants to move into integrating the online shopping cart with merchant’s POS systems.

“This new round of funding allows us to help merchants converge their offline and online sales through our POS and mobile POS integration, so they can sell their products anywhere at any time, offline or online, and from any device. We also will extend the rapid growth of our network of site-builder, CMS, hosting and payments partners globally,” said Ecwid president Jim O’Hara in an official statement.

Ecwid’s shopping cart is available in 175 countries and in 45 languages. The company says it now has more than 500,000 registered users.

Ecwid was founded in 2009 and is headquartered in Encinitas, Calif. ITech Capital led this funding round, with current investor Runa Capital also participating.