Varnish is a web accelerator / reverse proxy caching server.
http://varnish-software.com/
Web Servers · Varnish Server
Get access to data on 8,927,425 websites that are Varnish Customers. We know of 3,369,852 live websites using Varnish and an additional 5,557,573 sites that used Varnish historically and 1,188,852 websites in the United States.
Get a list of 8,927,425 websites using Varnish which includes location information, hosting data, contact details, 3,369,852 currently live websites and an additional 1,615,504 domains that redirect to sites in this list. 5,557,573 sites that used this technology previously and 1,188,852 websites in the United States currently using Varnish.