FedEx REST APIs (Express, US, OAuth 2.0)

The FedEx REST APIs at developer.fedex.com are the modern integration surface for FedEx Express in the US. They expose Ship, Rate, Track, Address Validation, and supporting operations as REST endpoints with JSON payloads, authenticated through OAuth 2.0 client_credentials. They are the default new-integration target and the API surface FedEx is investing in. The REST APIs run alongside the older FedEx Web Services SOAP product. Both still work today; FedEx has not announced a final SOAP sunset date as of this page's last review, but new contracts are typically issued on the REST surface and integrators should default to it. The two surfaces are not interchangeable: the REST APIs use JSON, OAuth tokens, and an updated error vocabulary, while the SOAP services use WSDL-driven envelopes and credentials embedded in the body. Operationally, the REST surface returns paginated results for tracking lookups, supports proactive notifications through FedEx's webhook product, and surfaces multi-piece shipment errors per piece rather than collapsing them into a single fault. Schema validation against the FedEx OpenAPI document before sending requests turns vague carrier errors into precise local failures and shortens incident loops. Sandbox returns deterministic test data; verify rate parity in production with a small parallel-running window before retiring any legacy code path.