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Every web server (sense 1) is running a web server program (sense 2).
The most common web or HTTP server programs are:
The most commonly-used web server program, Apache, with over 67% of market share as of October 2004, is available from the Apache Software Foundation.
See Web server software for a comprehensive list of HTTP server programs.
Although web server programs differ in detail, they all share some basic common features. Every web server program operates by accepting HTTP requests from the network, and providing an HTTP response to the requester. The HTTP response typically consists of an HTML document, but can also be a raw text file, an image, or some other type of document.
Usually these documents are stored on the web server's local file system. Both URLs and local filenames have a hierarchical structure, and the server maps the URL onto the local file system in a simple way. When web server software is installed and configured, the server administrator specifies a local pathname as the root from which the server software should locate files. For example, suppose we are configuring server software to provide HTTP service on a server whose IP addressAn IP address is a unique number, akin to a telephone number, used by machines (usually computers) to refer to each other when sending information through the Internet using the Internet Protocol. This allows machines passing the information onwards on be is example.funnycorp.com. We might set the server software's root directory to /home/public/web/. Then, if a web user enters the URL