What is an URL

As a Uniform Resource Locator (URL, GV “single source of indicator”) it refers to a type of Uniform Resource Identifiers (URIs). URLs identify and locate a resource on the used network protocol (e.g. HTTP or FTP) and the location of the resource in the computer. URLs represent the first and most common type of URI that defines the terms often used interchangeably. In everyday language URL is often used as a synonym for an Internet address. The URL for this article, for example is http://www.wikipedia.org/wiki/URL

Construction

Mandatory minimum components of a URL are the protocol, the host and the path. The latter consists of at least a slash (/), which refers to the main directory of the server.

Protocol

The used network protocol over which the resource can be localized. For example, the HTTP, HTTPS or FTP.

User/Password

If required, a login user name and password are transmitted. These are separated by a colon, the domain preceded by a divisive at sign (@). Although chosen for this example is the HTTP protocol the specification of a username and password as part of the URL currently is not part of the HTTP specification!

Current browsers accept this URL syntax, but ask the user whether they have registered with the specified data. Internet Explorer 6 (Windows XP SP2) has never been seen before by this URL syntax and it was flatly rejected as faulty. With a registry entry it can force the same behavior, as shown by its predecessors up to version 5.5.

This page unquestioned credentials and passed them directly to the server. In some other protocols such as FTP, it is an indication of the user data in the form shown, however, quite correctly are covered by the standards.

Host

The host, i.e. the Internet address of the host is controlled by the domain composition scheme. In its place can also be an IP address. The host www.example.org from the example above, consists of the top-level domain “org”, the second-level domain (example) and the third-level domain (www exists).

Port

The specification of the port allows the control of a TCP/IP ports. If no port is specified, the default port of the particular protocol is used – for example, HTTP 80, HTTPS 443, and with FTP 21st.

Url-path
The path describes a particular resource on the server. The path may be empty. An empty path can optionally be replaced by a trailing slash. The interpretation of supply (file or directory, text file, or run script) is left to the server. Often, a browser requests the path “/”, and instead gets the file “/ index.html back”, without this being apparent to the requesting client.

Searchpath

The URL can be separated, for example, in HTTP for the actual address with a question mark – a query string. So that additional information can be transmitted, the server side variables are assigned and processed.