What is Navigation start?
- Navigation start is the start point of a new pageload as far as performance tools are concerned.
- It is actually the moment just before a new page is requested.
- It is initiated by a user clicking a link or hitting enter after writing an url in a browser navigation bar.
Navigation start is a user initiated event beginning the process of going to a web page or resource.
Once this event occurs, a new page load has begun.
Why is navigation start measured?
Navigation start allows for more precise page load time measurement.
Before browsers reported this metric, there was no accurate "start point" to measure page load timing.
Navigation start is reported by the browser
As part of the Navigation timing API 1 used by most major browsers, navigation start is a widely used and understood metric.
Virtually all performance tools use this metric in some manner.
It is the start point of a new page load.