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A Uniform Resource Locator (URL) is a Uniform Resource Identifier (URI) that specifies where an identified resource is available and the mechanism for retrieving it.

A Uniform Resource Locator (URL) is a Uniform Resource Identifier (URI) that specifies where an identified resource is available and the mechanism for retrieving it.

In popular usage and in many technical documents and verbal discussions, URL is often incorrectly used as a synonym for URI. The best-known example of the use of URLs is for the addresses of web pages on the World Wide Web, such as https://codereview.stackexchange.com/.

The uniform resource locator was created in 1994 by Tim Berners-Lee and the URI working group of the Internet Engineering Task Force (IETF). The format is based on Unix file path syntax, where forward slashes are used to separate directory or folder and file or resource names. Conventions already existed where server names could be prepended to complete file paths, preceded by a double-slash (//).

File formats may also be specified using a final dot suffix, so that requests for file.html or file.txt may be served directly whereas file.php needs to be sent to a PHP pre-processor before the processed result is served to the end user. The exposure of such implementation-specific details in public URLs is becoming less common; the necessary information can be better specified and exchanged using Internet media type identifiers, previously known as MIME types.

Berners-Lee later regretted the use of dots to separate the parts of the domain name within URIs, wishing he had used slashes throughout. For example, http://www.example.com/path/to/name would have been written http:com/example/www/path/to/name. Berners-Lee has also said that, given the colon following the URI scheme, the two forward slashes before the domain name were also unnecessary.