H2O (web server)

H2O is a free and open-source web server. It is written in C, and is distributed under the terms of the MIT License.

It was designed with a focus on supporting HTTP/2 and TLS, maximizing the use of new web technologies such as prioritization and server push. As a result it achieves significantly better performance than conventional web servers such as nginx.

Features
H2O has the following key features:
 * HTTP/1.0 and HTTP/1.1 support
 * HTTP/2 support
 * Full support for dependency and weight-based prioritization with server-side tweaks
 * Cache-aware server push
 * HTTP/3 support (experimental)
 * TCP Fast Open
 * TLS support
 * Session resumption (standalone and memcached)
 * Session tickets with automatic key rollover
 * Automatic OCSP stapling
 * Forward secrecy and fast AEAD cipher suite
 * Private key protection using privilege separation
 * Encrypted Client Hello (experimental)
 * Static file serving
 * FastCGI support
 * Reverse proxy
 * Scripting using mruby (Rack-based)
 * Graceful restart and self-upgrade

History
In 2014-07, Kazuho Oku started development of H2O for usage as a server for mobile games while working at DeNA. The initial version was released in 2014-12, and the first stable version was released in 2015-02 when the HTTP/2 specification was finalized.