EasyPost Shipping API
Core REST API. Resources: Shipments (immutable; ship + buy rate), Rates, Addresses, Parcels, CustomsInfo, Forms, Labels (PNG/PDF/ZPL/EPL2), Pickups, ScanForms, Refunds, Batches, EndShippers, CarrierAccounts. Authentication uses your API key as HTTP Basic auth username (EASYPOST_API_KEY). Test and Production keys are issued separately.