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
Frequently asked questions
What is the Age HTTP header?
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.
Is Age a request or response header?
Age is a response header — the server sends it to the client. Set automatically by CDNs and reverse proxies.
What does a Age header look like?
A typical Age header looks like: Age: 24.
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
Declares a wall-clock deadline (HTTP-date) for how long the response stays fresh. Includes exact format, 4 production-ready server configs (Apache, Nginx, Express, CDNs), and the deprecation caveats with Cache-Control.
Vary
Which request headers cause different cached variants of the response.