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A common request from Rigor users is more granular control of alerting criteria for Real Browser Checks. We already provided the ability to specify a maximum page load time threshold via Threshold Monitors, and today we are extending that feature to include even more metric and comparison options.


We grouped the metrics into three categories: page, error, and resource. Page metrics include the following:

  • Server time
  • DOM load time
  • Page load time
  • Page size

Error metrics are aggregated over all resources, and include the following:

  • Client errors
  • Connection errors
  • Server errors
  • Total errors (sum of all other errors)

Resource metrics are also aggregated over all resources, and include the following:

  • CSS resources
  • Flash resources
  • HTML resources
  • Image resources
  • Javascript resources
  • Total resources (sum of all other resources plus uncategorized resources)


Previously, users were only able to make a “less than” comparison, i.e. the page load time should be less than a specific value. Now you can choose a “greater than” or “equal to” comparison.


This is a user-supplied field that refers to the time, size, or count of the metric. In case there is any doubt, the correct units are shown next to the value field.

Putting it all together

To add a Threshold Monitor:

  1. Create or edit a Real Browser Check
  2. Click on the Advanced tab and add a Threshold Monitor
  3. Select the metric, the comparison, and the value you want to compare against, and specify what pages you want to monitor

Screen Shot 2015-08-17 at 4.59.27 PM.png

In the example above, we have three Threshold Monitors set up for the check. The first one asserts that the page size should be less than 1,000,000 bytes. The second asserts that there should be no Flash resources loaded. The third asserts that the DOM load time should be greater than 100 milliseconds.


  • Do not try to add too many Threshold Monitors to one check. Instead, create a new check for each set of Threshold Monitors. We recommend using no more than three per check, but recognize that there are use cases that might call for more.
  • Counts are useful to guard against resource creep.
  • Try adding both a minimum and maximum value for time metrics. A time that is too low probably indicates that the site is not performing correctly, while a time that is too high indicates a slow site.
  • Set Total errors to 0 to be alerted whenever there is a resource that does not load.
  • Make sure that you do not add Threshold Monitors that are mutually exclusive. For example, you could create one that ensures that the page load time is greater than 200 milliseconds and one that ensures it is always less than 100 milliseconds.

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