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A bookmarklet to create page load waterfall in the browser using the Resource Timing API

Just add the bookmarklet below to your bookmarks bar.

javascript:(function(){var el=document.createElement('script');el.type='text/javascript';el.src='//';document.getElementsByTagName('body')[0].appendChild(el);})();

Works In*

IE 10, Chromium Nightly

*When I say 'works in' I mean you'll get a waterfall but sometimes there will be odd things about it!

To Do

  • Add DOM event markers e.g. onload etc.
  • Add AppCache, fix TCP times
  • Truncate URL display
  • Remove protocol from URL display
  • Fix blocked timings
  • Display blocked / active times for 3rd party resources
  • Check if bookmarklet script loaded before adding it
  • Add iframe support
  • Add tooltip with full URL and timing details
  • Add row number?
  • Add legend
  • Cleanup and refactor drawing code
  • Add Close button
  • Add Jdrop / HAR Storage links
  • Flexible width

To check

  • Why is the API sometimes unavailable in IE10?
  • "about:blank" in IE10 on - valid

Browser Issues

Here are the issues and queries found so far with the browser implementations of Resource Timing - no CORS testing so far.

(Convert these to GH issues???)


All of these issues are already marked as fixed on but waterfall code hasn't been tested against a recent build.


(no link to issue tracker for these)

  • Resource Timing is only available in IE9/IE10 document modes but during testing API wasn't present for some sites where it previously worked and a restart seemed to fix it. This needs re-checking to ensure it wasn't my error.
  • connectStart == connectEnd for both Navigation and Resource Timing entries - would expect different values for early page requests where new TCP connections would be opened.
  • Frequently domainLookupStart == domainLookupEnd even for domains the Windows VM has never seen previously.
  • responseStart == responseEnd in Navigation Timing for both first and repeat views even when waterfall in dev tools shows a response

Change Log

2013-01-01 Add JSDoc comments, start re-factoring drawing code


Bookmarklet that produces Page Load Waterfalls using the Resource Timing API



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