h2o/h2o

H2O - the optimized HTTP/1, HTTP/2, HTTP/3 server

CMIT11.4k879157723 open issues
Created Aug 16, 2014Last commit Feb 6, 2026Last human commit Jan 19, 2026
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H2O - an optimized HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3 (experimental)

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Copyright (c) 2014-2019 DeNA Co., Ltd., Kazuho Oku, Tatsuhiko Kubo, Domingo Alvarez Duarte, Nick Desaulniers, Marc Hörsken, Masahiro Nagano, Jeff Marrison, Daisuke Maki, Laurentiu Nicola, Justin Zhu, Tatsuhiro Tsujikawa, Ryosuke Matsumoto, Masaki TAGAWA, Masayoshi Takahashi, Chul-Woong Yang, Shota Fukumori, Satoh Hiroh, Fastly, Inc., David Carlier, Frederik Deweerdt, Jonathan Foote, Yannick Koechlin, Harrison Bowden, Kazantsev Mikhail

H2O is a new generation HTTP server. Not only is it very fast, it also provides much quicker response to end-users when compared to older generations of HTTP servers.

Written in C and licensed under the MIT License, it can also be used as a library.

For more information, please refer to the documentation at h2o.examp1e.net.

Reporting Security Issues

Please report vulnerabilities to h2o-vuln@googlegroups.com. See SECURITY.md for more information.

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