#status-codes

Every HTTP status code as an API. Look up any code (e.g. 404, 429, 503) and get its standard reason phrase, its class (1xx Informational, 2xx Success, 3xx Redirection, 4xx Client Error, 5xx Server Error), a plain-English description, the RFC that defines it, and handy flags for whether it is an error and whether it is commonly safe to retry (408, 425, 429, 500, 502, 503, 504). List every assigned code or filter by class, and enumerate the five status classes. Perfect for API clients and gateways, error pages, logging and monitoring dashboards, documentation and teaching. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 4 endpoints. Distinct from host/uptime checkers that report a live status — this is the reference dictionary of the codes themselves.

api.oanor.com/httpstatus-api

A clean, programmatic reference for HTTP semantics, built on the official IANA registries. Look up any status code with its reason phrase and class (404 → Not Found, Client Error; 503 → Service Unavailable, Server Error), list a whole class (4xx, 5xx…); look up any method with its safe/idempotent flags (GET → safe + idempotent, POST → neither, DELETE → idempotent); or look up / search the 255 registered HTTP header fields (Content-Type, Authorization, …) with their registration status. Ideal for API tooling, HTTP clients, documentation, linters, learning resources and error pages.

api.oanor.com/http-api