How to use curl command with http/2 on MacOS X

I am using a MacOS sierra (version 10.12.1). How do I use curl command with http2/ protocol? I am getting an error that read as follows:
            curl -I --http2
            curl: (1) Unsupported protocol
How do I solve this problem and use cURL with HTTP/2 on Mac OS X or MacOS Sierra?

The default version of curl does not support HTTP/2. Here is my current version on MacOS sierra:
$ curl --version
curl 7.49.1 (x86_64-apple-darwin16.0) libcurl/7.49.1 SecureTransport zlib/1.2.8
Protocols: dict file ftp ftps gopher http https imap imaps ldap ldaps pop3 pop3s rtsp smb smbs smtp smtps telnet tftp
Features: AsynchDNS IPv6 Largefile GSS-API Kerberos SPNEGO NTLM NTLM_WB SSL libz UnixSockets

So if I try to pass the --http2 option to curl command, I will get the following error on screen:
$ curl -I --http2
curl: (1) Unsupported protocol

Fixing curl: (1) Unsupported protocol error on MacOS

Use the brew command as follows to install curl with nghttp2. First, install Homebrew on macOS and then type the following brew command. nghttp2 is an implementation of HTTP/2 and its header compression algorithm HPACK in C. You need to compile and install cURL as follows:
$ brew update
$ brew upgrade
$ brew install curl --with-nghttp2

Sample outputs:

Fixing curl: (1) Unsupported protocol on Mac OS X

Please note down the path “/usr/local/Cellar/curl/7.50.3/bin/curl”

Create a shortlink in your ~/bin/

Type the following command:
$ mkdir $HOME/bin/
$ cd ~/bin/
$ ln -s /usr/local/Cellar/curl/7.50.3/bin/curl
$ ~/bin/curl --version

Sample outputs:

curl 7.50.3 (x86_64-apple-darwin16.1.0) libcurl/7.50.3 OpenSSL/1.0.2j zlib/1.2.8 nghttp2/1.16.0
Protocols: dict file ftp ftps gopher http https imap imaps ldap ldaps pop3 pop3s rtsp smb smbs smtp smtps telnet tftp 
Features: IPv6 Largefile NTLM NTLM_WB SSL libz TLS-SRP HTTP2 UnixSockets 

How do I test it?

Pass the --http2 flag to http2 enabled site:
$ ~/bin/curl -I --http2
Sample outputs:

HTTP/2 200 
server: nginx
date: Tue, 01 Nov 2016 21:59:18 GMT
content-type: text/html;charset=utf-8
vary: Accept-Encoding
cache-control: public,max-age=900,s-maxage=900,must-revalidate
expires: Tue, 01 Nov 2016 22:03:40 GMT
etag: de8af9a212f436d9d4d45f4cc994b2ca
last-modified: Mon, 05 Sep 2016 07:49:45 GMT
front-end-https: on
strict-transport-security: max-age=15768000
x-content-type-options: nosniff
x-frame-options: SAMEORIGIN
x-xss-protection: 1

A note about replacing the MacOS curl with updated version

You can create a softlink to the formula to replace the system cURL with PATH magic,
$ brew link curl --force
$ curl --version

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🐧 2 comments so far... add one

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2 comments… add one
  • Dave Nov 2, 2016 @ 18:53

    The macOS Sierra 10.12.1 curl has some additional features that you’ll lose if you build –with-nghttp2. The missing ones are: AsynchDNS, GSS-API, Kerberos, and SPNEGO (as listed in the ‘curl --version‘ output). To get HTTP/2 and the missing features too, use:

    $ brew install curl --with-nghttp2 --with-gssapi --with-c-ares

  • John Feb 17, 2021 @ 10:04

    This information is outdated. Now use

    brew install curl-openssl

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