Understating Customer Perceived Latency

Measuring web performance through end user’s lens

When we talk about web app’s performance there are many metrics that come into the picture like the load time, time to the first byte, time to contentful paint, etc.

Out of these, there are some metrics which talk about the network latency, the time a web page was waiting for the connection to be established & files/scripts to be served over the network & some metrics are specific to what happens after that, for example the time to first paint, first contentful paint, time to interact & first input delay.

Here are the standard timings that are reported by the browser window’s performance object

https://www.w3.org/TR/navigation-timing/timing-overview.png

Before we hit the page’s onLoad handler, all these happen, but this doesn’t include the latency that end users may perceive.

The real user’s perceived latency will most of the time be higher than the time for loadEventEnd after hitting a URL in the browser.

For an end-user, the page is useful & is loaded completly only when it is usable.

Time to interactive is when a web page’s content…