WebPagetest Forums
W3C User Timing - Question & are there other ways to do this? - Printable Version

+- WebPagetest Forums (https://www.webpagetest.org/forums)
+-- Forum: WebPagetest (/forumdisplay.php?fid=7)
+--- Forum: General Discussion (/forumdisplay.php?fid=25)
+--- Thread: W3C User Timing - Question & are there other ways to do this? (/showthread.php?tid=15555)



W3C User Timing - Question & are there other ways to do this? - chelvan - 11-21-2018 07:01 AM

Hi

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.

https://www.webpagetest.org/video/compare.php?tests=180830_3B_8e60cb8e1ff149a4c3cd9cc3d90accd5-r%3A1-c%3A0&thumbSize=200&ival=16.67&end=visual

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."

http://blog.patrickmeenan.com/2013/07/measuring-performance-of-user-experience.html

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

2. 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?
3. 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.