Netty is a non-blocking I/O client-server framework for the development of Java network applications such as protocol servers and clients.

[2] Netty includes an implementation of the reactor pattern of programming.

Besides being an asynchronous network application framework, Netty also includes built-in implementations of SSL/TLS, HTTP, HTTP/2, HTTP/3, WebSockets, DNS, Protocol Buffers, SPDY and other protocols.

Netty is not a Java web container, but is able to run inside one, and supports message compression.

[3] Beginning with version 4.0.0, Netty also supports the usage of NIO.2 as a backend, along with NIO and blocking Java sockets.