Directory
Curated links to specs, tools, carrier portals, and community resources for carrier API integration work.
The directory stays public for research and SEO. Pro unlocks deeper in-app challenge practice rather than gating this reference list.
Specifications & Standards
The definitive reference for HTTP methods, status codes, and semantics.
Standard format for machine-readable error responses.
Baseline OAuth 2.0 reference for carrier auth flows, token expiry, and refresh behavior.
Defines standard HTTP rate-limit fields that pair well with Retry-After and backpressure design.
Official SOAP 1.2 specification for understanding envelope, header, and fault structure.
Web Services Description Language specification for reading carrier service contracts.
Introductory XML Schema reference for type constraints, enums, and request validation in SOAP integrations.
Canonical SOAP message security reference for header-level auth and related metadata handling.
WS-Security profile reference for UsernameToken-based SOAP auth flows still used by legacy carrier stacks.
Tools
API development and testing platform. Essential for exploring carrier APIs manually.
Dedicated SOAP and REST testing tool. Import WSDLs to auto-generate test requests.
Network protocol analyzer for inspecting raw HTTP/SOAP traffic during debugging.
HTTP request/response testing service. Great for testing retry logic and error handling.
Official observability guidance for traces, metrics, and logs that support carrier incident runbooks.
Reference for separating liveness, readiness, and deeper dependency checks in production systems.
Carrier Developer Portals
Modern FedEx REST surface for Ship, Rate, Track, and Address Validation. OAuth 2.0 client_credentials.
Legacy FedEx SOAP/WSDL surface. Still operational at last review but new integrations should target the FedEx REST APIs.
Modern UPS REST surface for Shipping, Rating, Tracking, Address Validation, and Time in Transit. Replaces the legacy UPS XML/SOAP web services that were sunset on 2024-06-03.
DHL Express MyDHL API REST reference. Distinct product from DHL eCommerce and DHL Parcel DE. HTTP Basic over TLS.
REST API for DHL's domestic and cross-border parcel network in the Americas. Token-based auth, separate from MyDHL Express.
REST API for DHL Paket, Päckchen, and Warenpost shipments originating in Germany. Replaces the legacy Geschäftskundenversand SOAP/XML services.
DHL Freight's Sweden-specific REST hub for booking, pricing, validation, and shipping documents on Sweden domestic and Sweden-originating international road freight. Separate portal, base URLs, and credentials from MyDHL Express, DHL eCommerce Americas, and DHL Parcel DE.
Modern USPS REST surface for label creation, rate calculation, tracking, and address validation. OAuth 2.0 client_credentials. Replaces USPS Web Tools.
USPS's pre-OAuth XML-over-HTTP API. Deprecated in favor of the modern REST USPS APIs.
Royal Mail's REST shipping surface for UK origin shipments. Bearer-token auth issued through the Royal Mail Customer Portal.
La Poste Colissimo SOAP/WSDL surface for parcel shipments originating in France. French-language documentation primary.
REST surface for shipments originating in Australia on the Australia Post and StarTrack networks. API key plus account-number authentication.
Community Resources
Foundational article on the circuit breaker resilience pattern.
Deep dive into retry strategies with exponential backoff and jitter algorithms.
Best-in-class example of idempotency key implementation in a production API.
Concrete reference for raw-body signature verification, replay handling, and webhook troubleshooting.
XML diff and assertion tooling that is useful for SOAP contract tests and generated-envelope comparisons.