Linux / Unix: curl Command Pass Host Headers

How do I send a header to my Web server (such as Nginx / Lighttpd / Apache / ISS) on a Apple OS X or Unix or Linux based system using a curl command line option for testing and debugging my web apps or server nodes behind a load balancer?

Tutorial details
Difficulty level Easy
Root privileges No
Requirements curl command
Est. reading time 2 minutes
The curl command supports -H or --header option to pass extra HTTP header to use when getting a web page from your web server. You may specify any number of extra headers. When you add a custom header that has the same name as one of the internal ones curl would use, your externally set header will be used instead of the internal one. The syntax is:

curl -H 'YOUR-EXTRA-HEADER-HERE' apache-server-ip

For example, send Host header to to get HTML response from, run:

curl -H 'Host:'

This is also useful when has multiple virtual host set. The default is not to response anything when virtual host header is not sent:
$ curl -I
Sample outputs:

HTTP/1.1 500 Internal Server Error
Server: nginx
Date: Wed, 31 Oct 2012 18:51:03 GMT
Content-Type: text/html
Connection: keep-alive
X-Whom: l1-biz-cyber

Now, sent as Host header:
$ curl -I -H 'Host:'
Sample outputs:

HTTP/1.1 200 OK
Server: nginx
Date: Wed, 31 Oct 2012 18:52:20 GMT
Content-Type: text/html
Connection: keep-alive
X-Whom: l2-com-cyber
Vary: Cookie
Last-Modified: Wed, 31 Oct 2012 18:48:58 GMT
Cache-Control: max-age=98, must-revalidate
X-Galaxy: Andromeda-1
X-Origin-Type: DynamicViaDAL

You can use this command to test Apache server node behind a load balancer (only work with your own VLAN/LAN setup):

## see if apache node #1 is working or not ##
curl -I --header 'Host:' ''

Sample outputs:

HTTP/1.1 200 OK
X-Whom: l1-com-cyber
Vary: Cookie
Last-Modified: Wed, 31 Oct 2012 18:54:00 GMT
Cache-Control: max-age=77, must-revalidate
Content-type: text/html
Date: Wed, 31 Oct 2012 18:57:43 GMT
Server: lighttpd

This option can be used multiple times to add/replace/remove multiple headers:

curl \ 
-H "Accept-Language: en" \ 
-H "Host" \ 
-H "User-Agent: curl"

See curl command man page for more options:
$ man curl

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I'm Vivek Gite, and I write about Linux, macOS, Unix, IT, programming, infosec, and open source. Subscribe to my RSS feed or email newsletter for updates.

3 comments… add one
  • Ashish Jaiswal Nov 1, 2012 @ 1:58

    Plesase correct the url spelling “-sedning”

    • 🛡️ Vivek Gite (Author and Admin) nixCraft Nov 1, 2012 @ 6:01

      Thanks for the heads up!

  • Shantanu Gadgil Nov 7, 2012 @ 14:26

    HEDER should be HEADER

    :) :)

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