Causes for cache BYPASS

[operations3]

Hi,

We have two sites which are showing different behaviour. We are using “Cache-Control: no-cache” in our server response headers for all static assets (like css), so I’d expect to see cloudflare have a cache status of REVALIDATED for these assets, which is working for our devel site.

But for our staging site, the cache status for all our static assets is BYPASS, as below:

We have not implemented any page rules for these sites, so I presume this difference might come down to the headers coming back from the origin server? I’m hunting through them, but struggling to see the cause - Is there a definitive guide to what client and/or origin server behaviours could cause this site to always BYPASS?

Cheers,
Matt

[erictung]

Understanding Cloudflare's CDN

BYPASS: The origin server instructed Cloudflare to bypass cache via a Cache-Control header set to no-cache , private , or max-age=0 . BYPASS is returned when enabling Origin Cache-Control. Cloudflare also sets BYPASS when your origin web server sends cookies in the response header.

[operations3]

Much appreciated - I can see the issue now - it’s one of our AWS elastic load balancers which is setting a cookie in every response for the problem site, include static assets. So that’s convincing cloudflare to BYPASS.

Thank you @erictung !