How it works...

So, when you open any website for the first time it would return status 200 and will take some time to load the page because it will download each bit of the page. It all depends on your browser settings and cookies handler options.

When you would visit the same site next time, the latency period would be much lesser and it would return the 304 status code for the scripts or files, as shown in the following screenshot:

When the status is 200, the response header would show how much data is downloaded for a particular request. In the following screenshot, it shows 21501 bytes under the Content-Length attribute:

If the status code is 304, you will observe no data has been downloaded, as shown in the following screenshot:

Moreover, check the Expires section in the previous screenshot to get an idea of caching here.