HTTP2 with libcurl Spec: http://tools.ietf.org/html/draft-ietf-httpbis-http2 nghttp2 (https://github.com/tatsuhiro-t/nghttp2) libcurl uses this 3rd party library for the low level protocol handling parts. The reason for this is that HTTP2 is much more complex at that layer than HTTP1.1 (which we implement on our own) and that nghttp2 is an already existing and well functional library. Right now, nghttp2 implements http2 draft-09 Over an http:// URL If CURLOPT_HTTP_VERSION is set to CURL_HTTP_VERSION_2, libcurl will include an upgrade header in the initial request to the host to allow upgrading to http2. Possibly we can later introduce an option that will cause libcurl to fail if not possible to upgrade. Possibly we introduce an option that makes libcurl use http2 at once over http:// Over an https:// URL If CURLOPT_HTTP_VERSION is set to CURL_HTTP_VERSION_2, libcurl will use ALPN (or NPN) to negotiate which protocol to continue with. Possibly introduce an option that will cause libcurl to fail if not possible to use http2. Consider options to explicitly disable ALPN and/or NPN. SSL libs The challange is the ALPN and NPN support and all our different SSL backends. Right now we support ALPN and VPN with OpenSSL and ALPN with GnuTLS. Applications We hide http2's binary nature and convert received http2 traffic to headers in HTTP 1.1 style. This allows applications to work unmodified. curl tool curl offers the --http2 command line option to enable use of http2 To consider: - How to tell libcurl when using the multi interface that all or some of the handles are allowed to re-use the same physical connection. Can we just re-use existing pipelining logic?