A Uniform Resource Identifier (URI) is a string of characters that uniquely identifies a resource, which can be either abstract (like a concept) or physical (such as a document, image, or website) on the internet or other networks. The purpose of a URI is to provide a consistent way to distinguish one resource from another, regardless of whether or not that resource is accessible online.
URIs come in two main types:
- Uniform Resource Locators (URLs): These specify both the identity and the location of a resource, along with the method for retrieving it.
- Uniform Resource Names (URNs): These provide a unique name for a resource, independent of its location or how to access it.
Example of a URI:
urn:isbn:0451450523 (a book’s ISBN as a URN)
mailto:someone@example.com (an email address)
https://www.example.com/index.html (a URL identifying and locating a web page)
What Is a URL?
A Uniform Resource Locator (URL) is a specific type of URI that, in addition to identifying a resource, provides the means to locate and retrieve it by describing its primary access mechanism (such as the protocol) and its network location (such as a domain name and path).
Example of a URL:
https://www.example.com/index.html
This URL tells you:
The protocol: https
The domain: www.example.com
The path: /index.html
All URLs are URIs, but not all URIs are URLs. URLs are a subset of URIs that specifically provide the means to locate and retrieve a resource.
URIs identify; URLs locate. A URI might simply name a resource (like a book’s ISBN), while a URL tells you exactly where and how to access it (like a web address).