Caching · Response header
Age
How many seconds the response has been in a shared cache.
What is Age?
Age is added by intermediate caches (CDNs) to indicate how long the response has been sitting in cache. Combined with max-age, clients can compute remaining freshness.
Typical usage
Set automatically by CDNs and reverse proxies.
Examples
Age: 24Specification
RFC 9111 §5.1
Related headers
Cache-Control
Directives that control caching behavior.
Date
When the response was generated.
ETag
A version identifier for the resource — the backbone of conditional GETs.
Expires
Legacy: an absolute HTTP date when the response becomes stale.
Vary
Which request headers cause different cached variants of the response.