H2O (web server) explained

H2O
Released:	^[1]
Latest Release Version:	2.2.6
Latest Release Date:	^[2]
Programming Language:	C
Operating System:	Unix-like
Genre:	Web server
License:	MIT License

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.^[3]

Features

H2O has the following key features:^[4]

• 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)^[5]
• Static file serving
• FastCGI support
• Reverse proxy
• Scripting using mruby (Rack-based)
• Graceful restart and self-upgrade

History

In, started development of H2O for usage as a server for mobile games while working at DeNA.^[6] The initial version was released in, and the first stable version was released in when the HTTP/2 specification was finalized.^[7]

See also

• Fastly - The largest user of H2O in the world. Oku joined Fastly in .

Notes and References

1. Web site: H2O, the new HTTP server goes version 1.0.0 as HTTP/2 gets finalized. Kazuho Oku. 2015-02-19. Kazuho's Weblog. 2020-08-01.
2. Web site: Releases. GitHub. 2020-08-01.
3. Web site: Nginxより高速、HTTP/2サーバー「H2O」. 原田美穂. 2015-12-08. ＠IT. ja. 2020-08-01.
4. Web site: H2O - the optimized HTTP/2 server. DeNA. 2020-08-01.
5. Web site: Base Directives - Configure . live . https://web.archive.org/web/20230529045838/https://h2o.examp1e.net/configure/base_directives.html#ech . 2023-05-29 . 2023-07-18 . H2O - the optimized HTTP/2 server.
6. Web site: H2O - making HTTP better. Kazuho Oku. 2015-01-27. SlideShare. ja. 2020-08-01.
7. Web site: ウェブを速くするためにDeNAがやっていること - HTTP/2と、さらにその先. Kazuho Oku. 2016-02-05. SlideShare. ja. 2020-08-01.