H2O is a very fast HTTP server written in C. It can also be used as a library.

It supports:

- HTTP/1.0, HTTP/1.1
- HTTP/2
- persistent connections
- chunked encoding
- negotiation methods: NPN, ALPN, Upgrade, direct
- dependency and weight-based prioritization
- server push
- TLS up to 1.3
- support OpenSSL and LibreSSL
- forward secrecy
- AEAD ciphers
- OCSP stapling (automatically enabled)
- session resumption (internal memory)
- conditional GET using last-modified / etag
- mime-type configuration
- reverse proxy
- websocket support
- embedded mruby interpreter for high speed custom functions

WWW: https://github.com/h2o/h2o