Phusion Passenger - a.k.a. mod_rails or mod_rack - is a web server and application server, designed to be fast, robust and lightweight. Administration tools allow you to gain insight into web application operations and server performance.
Varnish is an HTTP accelerator designed for content-heavy dynamic web sites. In contrast to other web accelerators, such as Squid, which began life as a client-side cache, or Apache and nginx, which are primarily origin servers, Varnish was...
Varnish is leading in Top 10K Sites, Top 100K Sites, Top 1M Sites and The Entire Web.
In terms of market share, Phusion Passenger is clearly lagging behind, losing to Varnish in all segments.
Varnish has better usage coverage in more websites categories. Including Arts & Entertainment, Computers Electronics & Technology, Science & Education, Food & Drink and 20 other categories.
Phusion Passenger hasn't got a lead over Varnish in any websites category.
Varnish is leading in most countries, including United States, Japan, United Kingdom, France and 161 other countries.
Phusion Passenger is leading in Turkmenistan.