We're listing WooCommerce first because it's similar to Zen Cart in a few ways: it's free, open source, and can be installed on a hosted website. The primary difference in the installation procedure is that WooCommerce is a WordPress plugin and will need to be installed onto a website already using WordPress.

There are two ways to start building a WooCommerce online store. If you have a free WordPress.com account, an upgrade to WordPress's Business plan will be needed. On the other hand, if you have your own self-hosted website using the WordPress.org downloadable WordPress software, you can install WooCommerce by selecting it from the list of plugins.

WooCommerce has vast design flexibility, with tons of themes available for many industries — plus, these themes can all be customized. You can also extend WooCommerce's functionality with a wide assortment of plugins. However, the pricing of both themes and plugins varies, and while many are free, others (including some of the best) require a one-time fee or even a monthly payment. The plugins you choose also need to be rigorously checked before you add them to your website, as bugs or compatibility issues can bring your online store to a halt. Be sure to read all plugin documentation, and look at the user reviews as well, to identify any potential issues before you commit to adding them to your store.

Magento is another free, open-source eCommerce solution that can be installed on an existing web host, although Magento's software requirements are heavier than those of Zen Cart and you'll need a more powerful hosting package. It comes with tons of features, and Magento developers are readily available to perform any custom designing or programming you might need — although they're all third-party members of the community, and often come with a hefty price.

Magento is used by many retailers, but you should be aware that the size and complexity of the software often causes it to slow down once websites start to add larger numbers of products. Support can be hard to come by, and just like with any open-source solution, you're responsible for all updates and technical work on your store.

Shopify is one of the most popular eCommerce platforms in the world. Its most immediate difference from Zen Cart and the other previously listed alternatives is that, rather than being free and open source, Shopify is build on the SaaS (Software as a Service) model. This means that you simply create your Shopify account for a monthly fee and start building your store, without having to find separate providers for hosting and security. The monthly fee is more expensive than basic hosting, but covers everything instead.

Shopify is extremely user-friendly and makes it easy for anyone to get their online store up and running in a minimal timeframe. However, the platform does have several disadvantages: numerous features are missing, and many are only available by installing additional apps, each of which comes with a monthly fee. It's common to create a Shopify store for $29/month and quickly see your monthly expense double or triple as you discover more apps your business can't live without.

Additionally, Shopify charges transaction fees for every sale (on top of the usual fees imposed by the payment provider) unless you use their proprietary payment processor, Shopify Payments. Shopify Payments is based on Stripe and simply won't work for your business if you're not based in an approved country, or if you want to sell "high-risk" or heavily regulated products like CBD oil. Shopify has also been known to suspend businesses' use of Shopify Payments without warning, effectively closing the store and freezing collected payments.

BigCommerce is another SaaS eCommerce platform and is a direct competitor against Shopify. This means it includes hosting, updates, and other benefits of the SaaS model. It's not quite as easy to use as Shopify, but it has many more built-in features which reduce the need for additional apps. The slightly steeper learning curve comes from having so many more features available at the outset.

BigCommerce does have some disadvantages: mainly, the restrictive revenue tiers give you little control over which plan your store can use, and you may find your monthly bill increasing unexpectedly because you've reached a certain milestone in your sales volume. This plan upgrade often comes before a business can really afford it. However, unlike Shopify, BigCommerce does not charge transaction fees on your sales.

Volusion is similar to both Shopify and BigCommerce. It's another SaaS platform, and it's also quite user-friendly. While it doesn't have as many features as Shopify or BigCommerce, it does have some built-in advantages that Shopify doesn't, like a single-page checkout. It also has more built-in shipping carrier integrations than Shopify, and its monthly plans are a little cheaper.

Volusion's biggest disadvantage is its limited features, despite having a few things that Shopify doesn't, and it doesn't have much to offer that you couldn't get with another platform. Another consideration is that Volusion began charging transaction fees when it released its V2 version, and doesn't provide a way to avoid them in the way that Shopify does via Shopify Payments.