The Warning HTTP header — caching, RFC 9111, not observed in the catalog.
Warning
Caching obsoleted
A reference entry. The registry facts and catalog measurements below are complete; the written guidance for this header has not been authored yet.
Warning is caching — Headers that tell an intermediary what it may store and for how long. The oldest, best-specified corner of HTTP, and the one API providers most routinely ignore.
The registry
Listed in the IANA HTTP Field Name Registry as marked obsoleted in the registry — it should not appear in new work. Defined in RFC 9111, Section 5.5: HTTP Caching.
In the catalog
Registered with IANA and declared by not one of the 26,641 providers in the API Evangelist catalog. A registered field with no observed use is still part of the vocabulary — it just is not part of the practice.
Governed by these rules
Machine-enforceable governance rules from rules.apievangelist.com that apply to this header when it appears in an OpenAPI.
OpenAPI Components Headers Error error
Utilizing the headers object in the centralized OpenAPI components library helps make headers reusable across API requests and responses
Guidance: Rate Limits →OpenAPI Components Headers Info info
Utilizing the headers object in the centralized OpenAPI components library helps make headers reusable across API requests and responses
Guidance: Rate Limits →OpenAPI Headers Hyphenated Pascal Case error
HTTP headers should follow Hyphenated-Pascal-Case naming convention for consistency and readability, such as Content-Type, X-Request-Id, or Accept-Language.
Guidance: Naming →