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 531,194 websites that are Pingdom RUM Customers. We know of 27,828 live websites using Pingdom RUM and an additional 503,366 sites that used Pingdom RUM historically and 17,197 websites in the United States.
Get a list of 531,194 websites using Pingdom RUM which includes location information, hosting data, contact details, 27,828 currently live websites and an additional 334,287 domains that redirect to sites in this list. 503,366 sites that used this technology previously and 17,197 websites in the United States currently using Pingdom RUM.