How can I capture the browser rendering time?

  • I think you have two questions here. One is "Why can't LoadRunner capture render time?" and another is "How can I capture render time?" The answers are the same iff LoadRunner can actually capture render time.
    – corsiKa
    Commented Jun 13, 2013 at 15:31

4 Answers 4


Loadrunner is a tool that captures at a level below the browser (for example at the http level). It isn't a browser, and thus doesn't do any rendering that could be captured.

There are tools that hook into the browser itself (such as HTTPWatch). see: http://blog.httpwatch.com/2008/05/14/using-httpwatch-to-measure-page-load-times-for-new-and-existing-users/


The available tools vary by browser. Chrome has a built-in debugger; see https://developers.google.com/chrome-developer-tools/docs/timeline. For Firefox, see https://addons.mozilla.org/en-us/firefox/addon/yslow/.


Actually LoadRunner captures time all the way to the GUI quite well, it is called the GUI Virtual User. It has been in place since LoadRunner version 1.

GUI Time - Protocol layer time = Time in Client which includes client processing and rendering time.

  • 1
    But I think the original question is asking how to extract the rendering time out of "Time in Client" ("capture the browser rendering time") right? Commented Jul 8, 2013 at 18:41
  • There are counters that are being added by the w3c to account for rendering time in the client. Now, the bigger question, if IE renders faster than Firefox which renders slower than Opera but faster than Chrome, what is yoru reconciliation path to file a defect with Microsoft, Mozilla, Google or Opera to get the "rendering defect" fixed on your project timeline? My premise is that they are not really asking for rendering time, but the delta between when data arrives at the client versus when it is displayed, a value which includes client processing time Commented Jul 8, 2013 at 19:47

Just marketing a tool that R&D of my company (SendGrid) has developed for load testing, that you can give a try:


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