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The syntax of URIs

A URI is a string that refers to a resource.

The most common URIs are URLs, which identify the resource by giving its location on the Web.

A URL is composed of different parts; some are mandatory and others are optional.

Scheme or protocol

Example

http://example.com

http:// is the protocol.

It indicates which protocol (HTTP or HTTPS) the browser must use.

Authority

Example

http://example.com

www.example.com is the domain name, or authority, that governs the namespace.

It indicates which Web server is being requested.

Port

Example

http://www.example.com:80/path

:80 is the port.

  • It indicates the technical "gate" used to access the resources on the web server.
  • It is usually omitted if the web server uses the standard ports of the HTTP protocol (80 for HTTP and 443 for HTTPS) to grant access to its resources.

Path

Example

http://www.example.com:80/path/to/myfile.html?key1=value1

/path/to/myfile.html is the path to the resource on the Web server.

Previously, a path like this represented a physical file location on a web server. Now, it is mostly an abstraction handled by web servers without any physical reality.

Query

Example

http://www.example.com:80/path/to/myfile.html?key1=value1&key2=value2

  • key1=value1&key2=value2 are extra parameters provided to the web server.
  • The parameters are a list of key/value pairs separated with the & symbol.
    • Parameters define the search criteria used by the server to find a set of matching resources.
  • The ? before the key/value pairs indicates the start of the query string.

Fragment

Example

http://www.example.com:80/path/to/myfile.html?key1=value1&key2=value2#SomewhereInTheDocument

#SomewhereInTheDocument is an anchor to another part of the resource itself.

An anchor is similar to a "bookmark" inside the resource, giving the browser the directions to show the content located at that "bookmarked" spot.

Sources