As with most open source projects, it's very hard to get a measure of who/how/where/why Jetty is being used a deployed.  Downloads long ago became meaningless with the advent of many available bundling and distribution channels.   The Netcraft Web Survey is one good measure, as it scans the internet and identifies which server sites run. In the results released April 2008, Jetty is identified for 278,501 public server, which is 80% of the market share of our closest "competitor" tomcat (identified as coyote in the survey). Jetty is currently 12th in the league table of identified servers of all types and will be top 10 in 6 months if the current trajectory continues.

I normally don't like to paint Jetty as directly competitive to Tomcat, and instead focus more on the differences between the containers.  However, in this case there is a direct comparison as the Netcraft  numbers show the servers that are directly connected to the internet and using their own  HTTP implementations.  Jetty has been gaining on average 9000  such servers per month for the last 12 months!  (or 2500 per month since Jetty 2 first appeared in the survey in December 1998 - (Jetty-1 didn't serve an ID)). Obviously our features and flexibility are having good traction over the last decade!

Of course, this is not the full picture, as many more instances of the servers are deployed on private networks, are some of the 3 million servers that don't advertise their ID, or are proxied behind the 83 million Apache servers.  None the less, the servers that are directly connected is an interesting and important measure.  More over, given Jetty's flexibility and embeddability, we would expect a healthy ratio between public and hidden servers.  Jetty's inclusion in the Eclipse IDE from 3.3 probably gives us millions of installs alone, and we are used in many more projects and applications and an option for deployment in Geronimo, JBoss, JOnAS, and Glassfish EE servers. Of course these arguments mostly also apply to Tomcat and it too would have many hidden installations and almost certainly a greater proportion of the servers that are behind apache, but on this 1 measurable comparison I'll just have a little gloat at our continued gains.

The Jetty project continues to innovate and integrate, so we hope and expect to continue attracting new users:

•  Our asynchronous features are likely to be adopted by Servlet 3.0 and we will soon have a pre-release of Jetty-7 to  show them. 
  
• Jetty is available for the google android mobile phone and has created the possibility of micro servers in your pocket complete with web accessible media repositories, cameras and  PDA functions.
• Our OSGI and spring integration continues to improve.
• Our implementation of Cometd/Bayeux continues to improve and offer scalable Ajax Comet Push for Web 2.0 applications.
• The hightide bundle is providing a long term versioned supported distrobution.

We will be holding a Jetty Birds-of-a-feather session at JavaOne this May, so we invite all of those 278501 users to come along and hear about ongoing Jetty development and to tell others about their Jetty experiences.   Webtide will also have a booth at JavaOne, so please seek us out there if you want to hear about our commercial services and offerings.