The brand new thing is that you can test with multiple browsers with one run! Before I show you, there's one really IMPORTANT thing: the parameters have changed when you collect metrics, you choose which browser with the c parameter and the z decides how many runs per page (three is still the default value). It looks like this ( test the URL ten times with Chrome):

$ ./bin/sitespeed.io -u https://www.sitespeed.io -c chrome -z 10

If you want to test with multiple browsers, you add each browser separated with a comma:

$ ./bin/sitespeed.io -u https://www.sitespeed.io -c firefox,chrome 

Then you will get timings from both the browsers, by default fetching each URL three times. On the summary page, the summaries will be for both Firefox & Chrome: The metric summary data

All the summary timings will be named with the browser name at the end of the name. To get domContentLoadedTime for Firefox, you configure to fetch domContentLoadedTimeFirefox. Here's an exampe running on Windows, only showing domContentLoadedTime for each browser:

$ bin/sitespeed.io -u https://www.sitespeed.io -c firefox,chrome,ie -b domContentLoadedTimeFirefox,domContentLoadedTimeChrome,domContentLoadedTimeIE 

And the summary will then look something like this: Summary per browser

Running Internet Explorer on Windows have some caching issues (meaning the cache is not cleared between runs). If you have a good solution on how to solve that for Selenium, please send me or Tobias a tweet.

On the details page, you will see the data for each browser: The metrics from two browsers

Jenkins

If you are using the Jenkins plugin, you need to upgrade it to the new beta 7 version to be able to get all the browser metrics into Graphite. The summary metrics will look the same except that you will have an extra level per browser.

Remember that the metrics we fetch are synthetic measurements, it will not be the same for real users BUT if you fetch sufficient times (maybe 30 times per URL) then you can safely compare the timings between runs.
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See all the changes done in this release.