What's the difference between Jetty and Netty?

Jetty is a lightweight servlet container, easy to embed within a java application, there is an easy to use jetty client also.

Netty is an asynchronous event-driven network application framework.You can write your own servlet container or http client app with help of the Netty framework for example.

Edit:

Forgot to mention that Jetty 8 and Apache Tomcat 7 support servlet 3.0 spec, but netty doesn't. Because it's not a servlet container.

I think over time the overlap increases as both projects add new features.

Here is a benchmark: https://gist.github.com/dhanji/81ccc0e6652eccaf43cf

Jetty is a web server (HTTP), similar to the likes of Tomcat and such, but lighter than most servlet containers. This is closer to the traditional Java way of doing server applications (servlets, WAR files). Like Netty it is sufficiently lightweight to be embedded into Java applications.

Netty is a NIO client server framework which enables quick and easy development of network applications such as protocol servers and clients. It greatly simplifies and streamlines network programming such as TCP and UDP socket server. So Netty is focusing on helping to write NIO/non-blocking, asynchronous network programs.

If you deal a lot with network protocols and want it to be non-blocking use Netty (usually for high-performance cases). If you want a light HTTP servlet container use Jetty.

• Also see: Use Jetty or Netty?
• Alternatives to Netty: What are the Netty alternatives for high-performance networking?
• Articles about Netty: http://netty.io/wiki/related-articles.html
• Servlet 3.0 with Netty: http://www.jroller.com/agoubard/entry/run_servlets_with_netty#.Vtb0Teaunjs
• Servlet bridge for Netty: https://github.com/bigpuritz/netty-servlet-bridge

This is crude simplification, but it allows to understand the difference easily:

Netty is a framework to write TCP and UDP applications.

Jetty is a framework to write HTTP applications.