W3C User Timing - Question & are there other ways to do this?


I’ve read server articles on the W3C timing spec and the draft from W3C and am trying to get a better understanding of how it works. I know this is a basic question but I appreciate feedback on this as I’m trying to get our team to use User Timing.

Here are my questions:
In the W3C documentation it says “mark_above_the_fold” is
The time when all of the content in the visible viewport has been presented to the end-user as marked by the developer in their application.

  1. I am assuming that this means the actual point in time when the content was fully visible to the user as opposed to when it loaded? I am confused after looking at tests of some sites -

My concern is that after looking at some tests, I’m confused by the User timing results - in this test there is a mark for HeaderAreaBegin and HeaderArea End. In looking at the times, then comparing it to the filmstrip, it seems there is a lag in the rendering - that is I would have assumed that the HeaderArea begin would have been later since there is nothing in the filmstrip until 1300.


Patrick Meenan’s great article on this (link below) says “The library will record an aggregate “aft” time that is the point when everything that I consider critical as above-the-fold has loaded.”


So I’m now wondering if the marks just mean loaded as opposed to when it is displayed, which accounts for the lag time?

  1. Mark placement - In looking at how these marks are constructed on various sites, I assume that if I want to know when a div section such as the header has begun to display, I put the first mark e.g. beginHeader at the beginning of the div - and conversely another mark endHeader at the end of the div?
  2. Will the mark work if there are no images? We have a nav bar that has simply has a background in CSS (no image) and text. Does the timing mark know when the div begins to paint it is just has styling? I was just concerned since there are no images.