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One of the most underutilized and somewhat secret features in the Chrome browser is the built-in net-tools which is accessed by entering chrome://net-internals into your address bar. It will immediately begin to start capturing network data, which you can stop by going to Capture at the top and clicking stop. You are able to see just about every aspect of Chrome’s internals from this page including cache hits and misses. You can even see Chrome’s DNS cache on the DNS screen.

Among the various properties you are able to extract and analyze are:

Proxy, Events, Timeline, DNS, Sockets, Alt-Svc, HTTP/2, QUIC, SDCH, Cache, Modules, HSTS, Bandwidth, Prerender

Here is an example which illustrates that Chrome has hit an image in its cache which was originally served by my NGINX webserver configured with a custom HTTP header called “x-nginx-cache”. That field will always either contain a HIT or MISS value, depending if the client browser already has a copy of an object such as image or html data in its local cache due to loading the object at a previous point in time without the cached object expiring.

cache-control:max-age=864000
cf-ray:39ec36096f207942-LAX
content-encoding:gzip
content-type:text/html; charset=UTF-8
date:Fri, 15 Sep 2017 14:17:42 GMT
expires:Mon, 25 Sep 2017 14:17:42 GMT
link:<https://sysinfo.io/wp-json/>; rel="https://api.w.org/"
link:<https://wp.me/p2SXGn-hL>; rel=shortlink
pragma:no-cache
server:cloudflare-nginx
set-cookie:wfvt_947412895=59bbdf0586a7b; expires=Fri, 15-Sep-2017 14:39:09 GMT; Max-Age=1800; path=/; secure; HttpOnly
status:200
vary:Accept-Encoding
x-content-type-options:nosniff
x-nginx-cache:HIT

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