If you include an expiry date with a cache-control header then the server won't be contacted. I typically use this in combination with a unique suffix (for chan

If you include an expiry date with a cache-control header then the server won't be contacted. I typically use this in combination with a unique suffix (for changes) for my web applications. It appears that google are not doing that, they are indeed using these scripts to track your users. Take jquery for example: Response: Remote Address:[2a00:1450:4009:80a::200a]:443 Request URL:https://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js Request Method:GET Status Code:304 OK Response Headers: age:414824 alt-svc:quic=":443"; p="1"; ma=604800 alternate-protocol:443:quic,p=1 date:Tue, 29 Sep 2015 15:17:51 GMT expires:Wed, 28 Sep 2016 15:17:51 GMT server:GFE/2.0 status:304