HTTP - Host Header
Table of Contents
About
host in the context of HTTP is a header field that:
The Host field value is the network location of the origin server or gateway given by the original URL.
The value is:
- the host (ie ip name)
- and the port number (default to 80 for http and 443 for https)
Example
Example of a get request to the URL http://www.w3.org/pub/WWW/
GET /pub/WWW/ HTTP/1.1
Host: www.w3.org
Usage
It's used:
- to route the request to its destination server on the network.
- to host several domain on the same host (virtual domain)
Virtual Domain
One server (one host) can serve multiple domain thanks to the host header. The web server looks the value up and therefore can change the destination of the request. See What is and how works a virtual host / custom domain / vanity hostnames
Network Route
This value is used (generally with TCP/IP) to route the message to the destination server.
Gateway
It's also used to route the request to the destination website (A server may host several hostname called virtual host)
The http Server uses this value to create optionally virtual host.
On a Apache server for instance, the host value is mapped to the ServerName property of the configuration file in order to route the request to the backend web site.
Set
The host is an header that is set by the client in a request. The client sets it from the value found in the URL.
Documentation / Reference
Recommended Pages
HTTP - Request
An HTTP request is a message sent from a client to a server. It's the first part of a fetch, the second being the response. Structure A request message has: a first line called the