Shipping Modules give the store owner a way to change which shipping options are available to the customer at checkout time. During the checkout process, these modules are called to calculate the final shipping and packaging costs for the order.

The price can be affected by how many products have been ordered, how much they weigh, as well as any other configuration settings set either in the shipping module itself or in the administrative tool settings.

In addition to the default modules that come with osCommerce, there are many additions available in the community contributions for other shippers as well as other packaging scenarios.