Stale responses and invalidation
06Expiry does not always mean deletion. A state-changing success can require invalidation of a saved answer.
Related RFCs and changes
“Updates” changes part of an earlier RFC. “Obsoletes” replaces it. This list shows selected related documents.
DIAGRAM§ 4.2.4 ↗
RFC 9111 · § 4.2.4EXAMPLE
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Invalidate the changed target.
A non-error unsafe-method response triggers target-URI invalidation so later requests do not blindly reuse the old state.
Protocol participantThreat or exceptionProtocol controlSimplified drawings · precise section references
Read the updated RFC section ↗
Serving stale and invalidating are different decisions.
- A stale response needs a permitted circumstance such as disconnection or explicit permission, and must not violate a prohibiting directive.
- must-revalidate forbids reuse of a stale response without successful validation; if validation cannot be done, a 504 response is required.
- After a non-error response to an unsafe method, invalidate the target URI. Other URI invalidation is restricted by same-origin rules.
Invalidation means removing the saved entry or marking it invalid so validation is required, rather than guaranteeing every copy on the Internet was erased. RFC 5861 defines additional stale-response permissions.
Read the RFC section ↗Diagrams simplify the RFC. Read the linked sections for complete requirements.
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