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 614,142 websites that are Pingdom RUM Customers. We know of 36,970 live websites using Pingdom RUM and an additional 577,172 sites that used Pingdom RUM historically and 25,097 websites in the United States.
Get a list of 614,142 websites using Pingdom RUM which includes location information, hosting data, contact details, 36,970 currently live websites and an additional 498,213 domains that redirect to sites in this list. 577,172 sites that used this technology previously and 25,097 websites in the United States currently using Pingdom RUM.