This page contains information about web-based addresses called URLs.
What is a URL?
A URL, or Uniform Resource Locator, is the location of a file on the web. When you type the address of a web page into your browser, you are typing a URL. The most common format of a URL is illustrated by the URL of this page: http://www.cites.illinois.edu/101/url101.html. Here is a description of each part of the URL.
For more informtion, see IP Address on Wikipedia.
The first portion of the URL (http) designates the protocol that is used to locate the file or resource on the web.
A protocol is a standardized means of communication among machines across a network. Protocols allow data to be taken apart for faster transmission, transmitted, and then reassembled at the destination in the correct order.
Here, http represents the HyperText Transfer Protocol, which is used to transfer webpages across the Internet to web browsers such as Internet Explorer, Safari, Firefox, or Chrome. Other common protocols include https (for secure webpages—the s stands for "secure"), ftp (file transfer protocol), and news (for newsgroups).The protocol of a URL is followed by a colon and two slashes (://).
The portion of the URL following the protocol ("www.cites.illinois.edu") designates the host name of the computer you are accessing. The designator, www, found in many URLs, is an acronym for World Wide Web.
While using www is conventional, it is not necessary. Some web servers do not require www. For example, http://www.cnn.com and http://cnn.com both work. In the United States, the right-most designator (e.g., .com or .edu) describes the type of institution or organization displaying the information (See the Extensions Table for a list of possibilities for the right-most designator). In this example, illinois in this page's URL stands for the University of Illinois, which is an educational institution, or edu.
In every URL, after its server's host name (in this example, cites.illinois.edu), there is the name of the place where the page is stored in the website's directory structure (/101/), followed by the page's filename (/url101.html). A URL may have any number of directories following it. In this example, 101 is a directory under the root directory of the host you are accessing. The file url101.html is located in the 101 directory.
Institutions on the Web
The chart below refers to the type of institutions you may see while accessing the Internet in the United States. Other countries have abbreviated extensions, with the terminal portion of the host name defining the country in which the host resides. For example, http://www.bbc.co.uk is the web address for the commercial business (.co) called BBC residing in the United Kingdom (.uk). In the United States, domain names are distributed by a company named InterNIC, whose URL is http://www.internic.com.