About URLs
What is a URL?
The acronym URL stands for Uniform Resource Locator. Each time you log on to the web you see URLs but you may not have really noticed them. They appear in the Address box at the top of your browser either because you've typed them in, or because you've clicked on a link on a web page. On the web, the word Resource refers to anything available on the web, such as an HTML page, an image, a CGI script etc. A URL provides a standard way to locate these resources on the web.What does a URL consist of?
URLs that refer to http (hypertext transfer protocol), the protocol that web pages use, are made up of the elements shown below - some of which may be omitted.| Scheme | Host | Port | Path | Query | Fragment | |||||
| http | :// | www.smallbizonline.co.uk | : | 80 | / | scripts/page_1.php | ? | name=Fred | # | here |
The Scheme
This refers to the protocol and where a connection is made to request a web resource this will normally be http. If the connection is to a secure server it will be https and if the request is for a file resource, it will be ftp.The Host
This identifies the machine running as a web server. It's normally identified as a domain name which acts as an alias for the IP address of the machine.The Port
This is optional and if omitted assumes port 80 for http requests.The Path
This represents the location of the requested resource relative to the document root of the server. In the example URL above the requested resource is called page_1.php and is located in the directory, or folder, called scripts located in the document root.The Query string
This is used to pass additional information to the requested resource. In the example URL above, the variable name is set to the value "Fred" and passed to page_1.php. This is an example of a name-value pair where the name and value are separated by the equals sign. Additional name-value pairs can be sent by separating each with the ampersand character, as in this example. Name=Fred&age=26.The Fragment
This is used to refer to a specific section of a resource. In the case of HTML documents the fragment identifier refers to an anchor tag within the document so in the example URL above the fragment refers to an anchor tag within page_1.php thus<a name="here">An anchor</a>.
The fragment is used by the web browser, not by the web server, to cause the page section from the anchor downwards to be displayed at the top of the web browser window.
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