Tornado is a scalable, non-blocking web server and web application framework written in Python.

[2] It was developed for use by FriendFeed; the company was acquired by Facebook in 2009 and Tornado was open-sourced soon after.

[3] Tornado is noted for its high performance.

Its design enables handling a large number of concurrent connections (i.e., tries to solve the "C10k problem").

The following code shows a simple web application that displays "Hello World!"