Nghttp2

nghttp2 is a C library. It is an implementation of HTTP/2.

History
nghttp2 was created by Tatsuhiro Tsujikawa as a derivative of spdylay, an implementation of SPDY, a communications protocol created by Google in 2009, in C.

Several well-known projects use nghttp2 to implement HTTP/2, including Apache and cURL.

HTTP/2 implementation
nghttp2 will send a  frame upon consuming more than half of the flow control window. For instance, if the sender specifies the  [sic] as 65,535 octets in the   frame, nghttp2 will send a   frame upon exceeding 32,768 octets. The initial window size may be changed using the  and   flags.

Tools
nghttp2 offers multiple tools. nghttp is a command-line tool that uses nghttp2 to output HTTP/2 messages from a URL. nghttp's dependency-based priority is based on Firefox; when a connection is established, nghttp sends five  frames. Other tools provided include nghttpd, an HTTP/2 server, nghttpx, an HTTP/2 proxy, h2load, an HTTP/2 load testing tool, and inflatehd and deflatehd, tools to decompress and compress using the HPACK header compression algorithm.

nghttp3
nghttp3 is an implementation of HTTP/3 in C and authored by Tsujikawa. nghttp3 uses the QUIC network protocol designed by Jim Roskind at Google.