Install h2o with Homebrew, MacPorts, Nix, apt

Project links

• Homepage
• Repository
• Upstream docs
• Package manager page

Commands and aliases

• h2o

Project history

The H2O repository was created in August 2014. The README credits DeNA, Kazuho Oku, Tatsuhiko Kubo, and later contributors including Fastly, and describes H2O as an optimized HTTP server with HTTP/1.x, HTTP/2, and experimental HTTP/3 support.

H2O 1.0 arrived around the finalization of HTTP/2, and the Changes file records early work to support the finalized HTTP/2 version and fix issues reported by h2spec. The project subsequently added or refined TLS, OCSP, mruby scripting, FastCGI, reverse proxying, HTTP/2 priority behavior, server push, early hints, and libh2o APIs.

The release history shows a mature 2.x line through 2019, including security fixes for HTTP/2 denial-of-service vectors and other parser or logging issues. A 2026 repository release note records that maintainers had decided in 2019 to stop tagging regular versions, steering users toward the master branch instead of a backported stable-branch model.

Adoption history

H2O emerged as HTTP/2 moved from draft work into production deployment, so its adoption history is tied to operators and developers who wanted a server that handled HTTP/2 semantics deeply. The official site emphasizes lower CPU and memory-bandwidth use than older HTTP servers and highlights prioritization schemes, server push, and 103 Early Hints.

Fastly's public author page for Kazuho Oku identifies him as the author of H2O, quicly, and picoTLS, linking the server to a broader ecosystem of transport-layer and TLS work. Package-manager adoption through Homebrew, MacPorts, Nix, and Ubuntu made H2O available to developers experimenting with modern HTTP stacks without building from source.

How it is used

H2O can run as a standalone HTTP server or be used as libh2o. Its documentation covers command options, YAML-style configuration, virtual hosts, paths, static files, FastCGI, proxying, access logs, compression, mruby, HTTP/2, HTTP/3, and operational features such as graceful restart.

For CLI/package users, H2O is commonly installed to test or operate a compact web server with HTTP/2 and HTTP/3 behavior, to compare prioritization and push behavior, or to embed HTTP serving behavior through the library.

Why package nerds care

H2O is significant because it is not just another packaged web server: it captured a particular period when HTTP/2 implementers were validating new protocol semantics with h2spec, HPACK, prioritization trees, TLS choices, and server push. It also connected package ecosystems to related low-level projects such as picohttpparser, quicly, and picoTLS.

For people who follow formulae and ports, H2O is a useful example of a high-performance network daemon whose packaging surface spans daemon deployment, local protocol testing, and C library reuse.

Timeline

• 2014: H2O repository created.
• 2015: 1.0-era development aligned with finalized HTTP/2 support and h2spec fixes.
• 2017: 2.2.0 series added a broad set of server, proxy, mruby, and logging features.
• 2018: 2.3.0 beta added HTTP/2, proxy, mruby, TLS, and server-timing work.
• 2019: 2.2.6 and 2.3.0-beta2 included fixes for HTTP/2 denial-of-service CVEs.
• 2026: Release note documented the earlier decision to stop tagging versions and use master-branch commits.

Related projects

• Related projects include h2spec for conformance testing, nghttp2 as another major HTTP/2 implementation, picohttpparser as a parser used in the H2O ecosystem, quicly for QUIC, picoTLS for TLS, and web servers such as nginx and Apache that H2O is often compared with.

Sources

• https://formulae.brew.sh/formula/h2o
• https://github.com/h2o/h2o
• https://h2o.examp1e.net/
• https://h2o.examp1e.net/configure.html
• https://raw.githubusercontent.com/h2o/h2o/master/Changes
• https://raw.githubusercontent.com/h2o/h2o/master/README.md
• https://www.fastly.com/blog/author/kazuho-oku