Real User Monitoring gives insight into performance for actual users visiting the website.
https://www.pingdom.com/rum/
Analytics and Tracking · Application Performance
Get access to data on 611,433 websites that are Pingdom RUM Customers. We know of 28,839 live websites using Pingdom RUM and an additional 582,594 sites that used Pingdom RUM historically and 17,484 websites in the United States.
Get a list of 611,433 websites using Pingdom RUM which includes location information, hosting data, contact details, 28,839 currently live websites and an additional 508,437 domains that redirect to sites in this list. 582,594 sites that used this technology previously and 17,484 websites in the United States currently using Pingdom RUM.