HTTP/2 Protocol Implementation for the Crystal Language
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ysbaddaden CI: run 'apk update'
Otherwise we may try to install old openssl packages that are no
longer available.
Latest commit 5db786e Apr 10, 2018


A pure Crystal (but incomplete) implementation of the HTTP/2 protocol.

Requires OpenSSL 1.1 or above to support ALPN protocol negotiation, which is required for HTTP/2 over secure connections.


  • HPACK (including DH compression)

  • HTTP/2 connection, streams, frames, ...

  • HTTP/2 flow control (in/out, whole-connection, per-stream)

  • HTTP/2 priority

  • support HTTP/2 server connections

  • integrate transparently into HTTP::Server (broken)

  • integrate into HTTP::Server::Context (http version, server-push)

  • support HTTP/2 client connections

  • integrate into HTTP::Client

  • HPACK tests (HTTP/2 protocol, ...)

  • HTTP/2 server unit tests (HTTP/2 protocol, ...)

  • HTTP/2 client unit tests (HTTP/2 protocol, ...)

  • h2spec


Build and run the bin/server server, then launch h2spec.

$ make bin/server

Test against HTTP:

$ bin/server
$ ./h2spec -p 9292 -S

Test against HTTPS:

$ TLS=true bin/server
$ ./h2spec -p 9292 -k -t -S



  • rfc7540 HTTP/2
  • rfc7541 HPACK Header Compression for HTTP/2


  • rfc1945 HTTP/1.0 (informational)
  • rfc2616 HTTP/1.1 (obsolete)
  • rfc7230 HTTP/1.1 Message Syntax and Routing
  • rfc7231 HTTP/1.1 Semantics and Content
  • rfc7232 HTTP/1.1 Conditional Requests
  • rfc7233 HTTP/1.1 Range Requests
  • rfc7234 HTTP/1.1 Caching
  • rfc7235 HTTP/1.1 Authentification