HTTP Caching

Updated 18 Sep 2026

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What it is
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  storing HTTP responses for reuse when cache rules permit
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Kinds
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  private cache — serves one user, commonly within a browser
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  shared cache — can serve multiple useres, such as proxy or CDN
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Ordinary flow
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  reusable fresh response -> serve from cache
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  validation required and validator available -> send a conditional request
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  no usable resopnse or validator -> retrieve the representation
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Freshness
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  “fresh” means reusable according to HTTP freshness rules
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  it does not prove that the application publisher has not deployed a newer version
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  stale responses require validation or another explicitly permitted reuse condition
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Variation
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  Vary identifies request fields that affect representation selection
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References
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  https://www.rfc-editor.org/rfc/rfc9111.html
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Related
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  Cache-Control
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  Unavailable reference

Linked references 5