OnLoad time measures what aspect of website performance?

OnLoad time primarily measures the time spent processing the load event. This includes the period from when the browser starts to load the page until all the resources on that page—such as images, scripts, and CSS files—have been fully loaded and rendered.

In the context of web performance, OnLoad time signifies how long it takes for the page to become usable from a user's perspective. This measure does not solely account for the loading of resources or the network latency involved in fetching those resources. Instead, it focuses on the event that signifies that the browser has completed loading all the necessary components to present the page fully to the user.

While the other options touch on various aspects of website performance, they do not accurately capture what OnLoad time specifically accounts for. For example, the time spent on initial loading of resources encompasses a wider range of loading times, and total time from request to rendering would involve factors beyond the load event itself. Thus, processing the load event is the most precise representation of what OnLoad time measures in terms of overall page performance.