RFC 9111 / CACHE POLICY

Cache-Control directives

Directives separately control storage, validation, freshness, transformation, and shared-cache behavior.

Related RFCs and changes

“Updates” changes part of an earlier RFC. “Obsoletes” replaces it. This list shows selected related documents.

DIAGRAM§ 5.2.2 ↗

RFC 9111 · § 5.2.2EXAMPLE

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Bound the lifetime.

This alternative policy provides a 60-second freshness lifetime, subject to other applicable constraints.

Protocol participantThreat or exceptionProtocol controlSimplified drawings · precise section references

WHAT CHANGED

RFC 7234 caching directivesRFC 9111 §5.2.2.3

RFC 9111 introduces must-understand. Appendix B also records that the Warning response field is obsolete; the main cache requirements still apply.

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KEY POINT

Read the exact directive rather than guessing from its name.

Unqualified no-cache permits storage but requires successful validation before reuse.
no-store normally prohibits storing the request/response data covered by the directive; max-age bounds freshness.
must-understand restricts storage to caches that understand the response status’s caching requirements; its specified behavior can override no-store.

DETAILS

no-store is not a complete privacy guarantee: it cannot erase copies already obtained or protect against malicious caches. The qualified no-cache form has field-specific rules; this example uses the unqualified form.

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Diagrams simplify the RFC. Read the linked sections for complete requirements.

Privacy

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