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H2O

On the record

Binary packages
Binary packages are listed for FreeBSD, Homebrew on macOS, RPM distributions including Fedora, RHEL/CentOS and OpenSUSE, and Docker.h2o.examp1e.net · read 1 Oct 2026
Dependencies
Building the standalone server requires a C/C++ compiler, CMake, pkg-config, OpenSSL 1.0.2 or later or a compatible TLS stack, and zlib.h2o.examp1e.net · read 2 Oct 2026
Deployment
The install guide documents building from source with CMake and lists binary packages for FreeBSD, macOS Homebrew, several RPM distributions, and Docker.h2o.examp1e.net · read 2 Oct 2026
Disclosure policy
After acknowledgement, the project uses a 90-day public-disclosure window followed by a possible 14-day grace period.github.com · read 1 Oct 2026
HTTP/2
HTTP/2 support includes dependency- and weight-based prioritization and cache-aware server push.h2o.examp1e.net · read 1 Oct 2026
HTTP/2 and HTTP/3
Features include HTTP/2 prioritization and cache-aware server push, plus HTTP/3 Extensible Priorities and a fusion AES-GCM engine for QUIC packet generation.h2o.examp1e.net · read 2 Oct 2026
HTTP/3
HTTP/3 support includes Extensible Priorities and a fusion AES-GCM engine for QUIC packet generation.h2o.examp1e.net · read 1 Oct 2026
Installation
Source installation requires a C or C++ compiler, CMake, pkg-config, OpenSSL 1.0.2 or later, and zlib.h2o.examp1e.net · read 1 Oct 2026
Library
H2O is also available as the libh2o software library.h2o.examp1e.net · read 1 Oct 2026
Library use
H2O can also be used as the libh2o software library; building it requires libuv 1.0 or above and OpenSSL 1.0.2 or above.h2o.examp1e.net · read 2 Oct 2026
License
The FAQ states that H2O is licensed under the MIT license.h2o.examp1e.net · read 2 Oct 2026
Other capabilities
H2O supports static file serving, FastCGI, reverse proxying, mruby scripting, graceful restart, and self-upgrade.h2o.examp1e.net · read 2 Oct 2026
Performance
The maker says H2O provides quicker responses with less CPU and memory-bandwidth use than older-generation web servers.h2o.examp1e.net · read 2 Oct 2026
Purpose
H2O is an optimized HTTP server supporting HTTP/1.x, HTTP/2, and HTTP/3.h2o.examp1e.net · read 2 Oct 2026
Release policy
Since April 2023, H2O has ceased version releases and treats each master-branch commit as stable except features marked experimental.h2o.examp1e.net · read 1 Oct 2026
Release status
The install page says H2O ceased releasing versions as of April 2023 and treats each master-branch commit as stable except features marked experimental.h2o.examp1e.net · read 2 Oct 2026
Scripting
H2O can be scripted using mruby with Rack-based support.h2o.examp1e.net · read 1 Oct 2026
Security
The repository has a security advisories page listing reported vulnerabilities and fixes, and asks users to report vulnerabilities by email.github.com · read 2 Oct 2026

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