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A Uniform Resource Locator (URL) specifies the location and method of accessing an object on the internet. It includes a protocol name, network path, and optional queries and fragment identifiers. The term URL is often used interchangeably with Uniform Resource Identifier (URI), which can refer to a URN identity, URL address, or both. A URL consists of a URI scheme and schema-specific components. Search engines and web browsers use URL normalization to determine if multiple URLs refer to the same object.
A Uniform Resource Locator, also known by the acronym URL, is a means of specifying the location and method of accessing an object on the Internet. Includes a pattern or protocol name that describes how to access the object. It also includes the network path, along with optional queries and fragment identifiers. A very common use of a URL is to point a browser to a website.
The original concept of the Uniform Resource Locator evolved during the early 1990s. Request For Comments (RFC) 1630 was the first URL standard, released by the Internet Engineering Task Force (IETF) in 1994. A name without an associated location or access method became known as a Uniform Resource Name (URN). By combining the two concepts, the term URI (Uniform Resource Identifier) was born. A URI can be a URN identity, a URL address, or both. It can also refer to an object that is not network based at all.
In technical circles, the term Uniform Resource Locator is rarely used longer – the URI is preferred. However, URL remains a popular name among the general public and the press. The latest URI specification, released in 2009 as RFC 3986, clarifies the concepts of URL, URN and URI.
A Uniform Resource Locator consists of two parts. The first is the name of a URI scheme, followed by a colon. A schema defines the protocol or other method used to access the resource. The Internet Assigned Numbers Authority (IANA) maintains a long list of registered URI schemes. Hypertext Transport Protocol (HTTP), Secure HTTP (HTTPS), and File Transport Protocol (FTP) are probably the most common. Many unregistered schemes are also used.
The second part of a Uniform Resource Locator is schema-specific and can include several components. This part of an HTTP URL often starts with www. followed by a domain name. An Internet Protocol (IP) numerical address can be used in place of the domain name. The name can be followed by the path to a specific object. There may also be a query string, the name of a fragment header within the object, or both.
When typing a web page URL into a browser, the schema and part of the domain name are often optional. If omitted, “http://” or “http://www”. it is usually assumed by the web browser. The path, query, or fragment can also contain limited special characters in hexadecimal number format. A space—%20—is most commonly used. An internationalized resource identifier (IRI) also allows Unicode characters throughout.
More than one unique Uniform Resource Locator can describe a path to the same object. Search engines can use a process called URL normalization to determine if multiple URLs actually refer to the same thing. Web browsers and crawlers do this too. A URL can also point to an object that cannot be found: it has been moved or it never existed.
