page speed
how long people wait
Page speed is two separate questions that get collapsed into one number everywhere else. How long before the server says anything, and how much it then makes the browser fetch.
About this check
·Two questions, not one
A server that thinks for 800ms before sending a byte is slow in a way no amount of image compression fixes. A server that answers instantly and then sends four megabytes is slow in a different way. The first is caching and hosting; the second is what is on the page. They are separated here because they are fixed by different people on different days.
·Measured from the outside, on the first visit
This is what the page costs someone arriving cold, with nothing cached, which is every search visitor you have. Your own second load tells you almost nothing — by then the browser already holds most of it.
·What this does not use
There is no Lighthouse score here. A lab score run from one machine on one connection is a useful development tool and a poor description of what your visitors experience. What is measured is the response itself: the time to the first byte, the bytes that follow, and how many separate things the browser is asked to go and get.