USPS Web Portal
Free Ecommerce Website Shipping and Shopping Cart APIs
The USPS Web Tools® API library gives ecommerce website shopping carts and shipping software access to valuable USPS® data—free of charge! You can check shipping rates, track packages, and schedule a package pickup all through USPS Web Tools. Save time and money by reducing shipping errors due to incorrect address entries. This tool corrects errors in street addresses, including abbreviations and missing information. It also supplies a ZIP+4® Code.