As of today, newly created Sites will have 2 Test Profiles: PageSpeed Desktop and PageSpeed Mobile.
PageSpeed Desktop and PageSpeed Mobile Test Profiles run on Calibre infrastructure using the same simulated networking conditions as Google PageSpeed Insights.
Prior to this change, new Sites were created with Test Profiles using runtime network throttling. Simulated throttling comes with the added benefit of tests that complete faster, so you can get results quicker.
The new defaults are designed to provide a test environment that is more consistent with Google’s PageSpeed, while still encompassing the power and flexibility of Calibre's configurable synthetic monitoring platform.
This change will not affect existing Sites, however you can switch between Test Profile devices at any time by navigating to Site Settings → Test Profiles. Runtime network throttling is still available for all Sites.
New Sites created using Node.js API or Command-Line Client (CLI) will use these new default Test Profiles. You can optionally specify Test Profile settings when creating a Site using the API. if that’s more suitable for your workflow.
For more information on Test Profiles, see the Test Profile documentation.