How Age works
Browsers subtract it from max-age, so a response cached for 50 seconds of a 60-second max-age is only fresh for 10 more seconds. Seeing Age in a response is a quick way to confirm a CDN served it from cache; Age: 0 or no Age usually means it came from the origin.
Examples
Age: 3127Check it
curl -sI https://example.com | grep -i '^age:'Paste a full set of response headers into the HTTP header checker to get every header explained and common mistakes flagged.
Related headers
- Cache-Control: tells browsers, CDNs and proxies whether a response may be stored, by whom, and for how long.
- Expires: gives an absolute date after which the response is stale.
- Vary: lists the request headers that change the response, so caches keep a separate copy for each value.
More caching headers
ETag , If-None-Match , Last-Modified , If-Modified-Since .
Sources
Spotted a mistake? Email hello@devtoolsmith.com and we’ll fix it.
Frequently asked questions
What does the Age header do?
The Age response header tells how many seconds a response has spent in a cache (usually a CDN) since it was fetched from the origin. Browsers subtract it from max-age, so a response cached for 50 seconds of a 60-second max-age is only fresh for 10 more seconds. Seeing Age in a response is a quick way to confirm a CDN served it from cache; Age: 0 or no Age usually means it came from the origin.
How do I see the Age header?
Run "curl -sI https://example.com" to print a response’s headers, or open the Network tab in your browser’s dev tools and select the request. Paste the headers into the HTTP header checker on this site to get each one explained.