Real User Monitoring (RUM) is the ability to measure the performance of your website/web application as seen by your end users. Some of the measurements are well-supported, some are browser-specific, and a few standards allow observability by letting you decide the measurement parameters. In the plethora of tools, it is hard to understand the differences. With this post, I would like to provide you a firm foundation on the minimum supported provided by the RUM solution for some solid measurements.
Navigation Timing API
In the old days of the wild-wild west, the performance measurements were instrumented using custom JavaScript code. The challenge was the measurement would begin only after the base HTML was downloaded and the JS code executed.