Age
ResponseActiveThe Age header tells the client how many seconds the response has been in a proxy cache. Age: 0 means the response is fresh from the origin. Age: 3600 means it was cached 1 hour ago. Clients use Age to determine effective cache freshness: a response with max-age=86400 and Age=80000 only has 6400 seconds of freshness remaining.
Age: <delta-seconds>
Description
Age is set by caches (CDNs, reverse proxies) to indicate how long the cached response has been stored. It allows clients to calculate the remaining freshness life: remaining = max-age - Age. If Age exceeds max-age, the response is stale and the cache must revalidate. Age is monotonically increasing – a CDN with Age: 3600 will deliver Age: 3601 to the next client one second later.
Examples
Fresh cache hit
http
HTTP/1.1 200 OK
Cache-Control: max-age=86400
Age: 3600
X-Cache: HIT
# Remaining freshness: 86400 - 3600 = 82800 secondsNearly stale
http
HTTP/1.1 200 OK
Cache-Control: max-age=3600
Age: 3580
X-Cache: HIT
# Remaining freshness: 20 seconds – stale soon