Store and select a response
01A cache first decides whether storage is permitted, then whether a stored response matches a later request.
Related RFCs and changes
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DIAGRAM§ 3 ↗
RFC 9111 · § 3EXAMPLE
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03
Choose the matching stored variant.
A JSON-preferring request must not accidentally receive a variant selected for HTML.
Protocol participantThreat or exceptionProtocol controlSimplified drawings · precise section references
Read the updated RFC section ↗
A stored answer still needs a valid reuse decision.
- Storage requires the understood method and applicable status, directive, and authentication conditions in §3.
- The primary cache key includes method and target URI; common GET caches often key primarily by URI.
- Vary requires comparing the nominated request fields before selecting a stored variant. Vary: * never matches without validation.
A cache can decline to store an otherwise cacheable response. Partial and authenticated responses have additional rules. The diagram shows an eligible ordinary GET response.
Read the RFC section ↗Diagrams simplify the RFC. Read the linked sections for complete requirements.
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