Almost identical, occasionally cheaper. CoreCommerce supports 99% of BigCommerce features, payment gateways and shopping methods. It also has one of the best product import processes and tool suite sof any hosted shopping cart. You should have no problem moving from BigCommerce to CoreCommerce.
CoreCommerce is the best alternative for people outside the United States and Canada (or inside the USA and Canada) because of the wide variety of shipping and payment providers it supports.
Americommerce supports all the same features as BigCommerce and adds several new ones including multistore capabilities, email newsletter management and built in affiliate program. You could easy save money by moving to Americommerce from BigCommerce and the support staff are happy to help you organise the product import.
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A great alternative to BigCommerce for Americans and Canadians, a very good cart but it only supports FedEx, UPS, USPS and Canada Post for shipping so the rest of the world might struggle to make it work. It supports all other BigCommerce features and adds some wonderful marketing, direct marketing and re-marketing tools as well.
Very underated. 3dCart is a great alternative to BigCommerce. If you are not in North America you will have trouble finding a compatible shipping provider because 3dCart only supports UPS, FedEx, USPS, DHL and Canada Post. Otherwise the only missing feature is Wish lists.
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You can add the necessary features to Shopify from the Shopify AppStore to make it generally compatible with BigCommerce. The only limitation would that it will end up costing you more, add to that the 2% per transaction fee Shopify add to your monthly bill and the costs increase again.