HTTP reference

Status codes: every registered code with its meaning, when you typically see it, whether to retry, whether it is cacheable by default, and its RFC. Search by number or words ("rate limit", "redirect", "proxy").

REST design: a searchable guide to designing HTTP APIs — method semantics, which status code to return when, resource naming, pagination (offset, cursor, Link headers), filtering and sorting, versioning and deprecation headers, RFC 9457 problem-details error bodies, idempotency keys, ETags and optimistic concurrency, rate-limit headers, caching, hypermedia, authentication and OAuth 2 flows, REST vs GraphQL vs gRPC, and an OpenAPI quick reference.

Headers: purpose, example, and CORS notes for the common request and response headers.

Methods: safe, idempotent, and cacheable properties of each method.

Cache-Control: paste a header value (or pick a preset) for a plain-English summary of how browsers and CDNs will treat the response, each directive explained, and warnings about contradictions.

CORS: when browsers send a preflight, what the exchange looks like, how to fix the usual errors, and server snippets.

MIME types: file extensions and their content types.