What is host header?

The host header is the third piece of information that you can use in addition to the IP address and port number to uniquely identify a Web domain.

Microsoft called a host header as an application server (An application server is a software framework that provides both facilities to create web applications and a server environment to run them.) IIS (internet information server) supports multiple Web Site on a single server.

To create and host multiple Web sites, you must configure a unique identity for each site on the server. To assign a unique identity, distinguish each Web site with at least one of three unique identifiers: an IP address, or a TCP port number or a host header name.

To host more than one web site on a web server, you can assign a unique IP address to each Web site, designate a non-standard TCP port number for a Web site, or use host headers.

It is nothing but providing a related name as the URL for the web application, by default SharePoint takes only the local server name as a URL and then renders the data’s from the content database.

Multiple host headers (and IIS bindings) are allowed; you can use alternate access mappings to specify additional URLs on which the same content will be served. If you add alternate access mappings after the default zone created during the web application creation, you must manually add the IIS bindings.

The Host request header specifies the domain name of the server (for virtual hosting), and (optionally) the TCP port number on which the server is listening.

If no port is given, the default port for the service requested (e.g., “80” for an HTTP URL) is implied.

A Host header field must be sent in all HTTP/1.1 request messages. A 400 (Bad Request) status code will be sent to any HTTP/1.1 request message that lacks a Host header field or contains more than one.

For example, the host header name for the URL https://www.spguides.com is www.sharepointsky.com. An HTML 3.0 or later browser supports HTTP 1.1. The browser includes the host header name you specified in the location field of the request header that the browser sends to the server.

Host header is used to administer multiple domains with a single IP address.


Host: <host>:<port>


<Host> the domain name of the server (for virtual hosting).
<Port> TCP port number on which the server is listening.

The importance of giving the host header while creating the web application:

The main benefit of assigning a host header to a web application is that in the frequent case that you have more than one web front-end server servicing HTTP requests for your SharePoint sites, you can easily use the host header to address the desired sites and let your load balancing appliance (or NLB configuration) choose one of the front-end to which forward the incoming request.

Host Headers advantage:

  • Organizations that host multiple web sites on a single server often use host headers because this method enables them to create multiple Web site identities without using a unique IP address for each site.
  • Host Headers are cost-effective as reserving public IP addresses cost money.
  • Manageability is another great advantage if you host too many sites under the same IIS server.
  • DNS configuration and server configuration are much easy to manage.

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