Jetty vs Netty

TL;DR

• Netty: to deal with network protocols; non-blocking, high-performance. Used by distributed data processing frameworks like Apache Spark, Presto, Cassandra, Akka; also by gRPC.
• Jetty: a light HTTP servlet container. Similar to Tomcat; SpringBoot uses Tomcat by default but can be changed to use Jetty.

More Details

What is a servlet container:

• also known as a web container.
• a servlet receives a request and generate a response
• a Servlet Container manages the lifecycle of servlets, mapping URL to servlet; part of a web server.
• examples: Tomcat, GlassFish, JBoss, etc.
• Servlet API: javax.servlet

Even though the names of "Netty" and "Jetty" look confusingly similar, they are essentially 2 different things:

• Jetty is a lightweight servlet container, originated from Eclipse, easy to embed within a java application.
• Netty is an asynchronous, event-driven, non-blocking I/O, network application framework. Netty can run inside a servlet container.

Official Websites

• Netty: https://netty.io/
• Jetty: http://www.eclipse.org/jetty/