Uniform Resource Identifier (URI)
A URI uniquely identifies or names a resource on the Internet; it defines a standard syntax (scheme, authority, path, query, fragment) and the distinction from URLs and URNs.
A Uniform Resource Identifier (URI) is a standardized string of characters used to identify or name a resource on the Internet or in other information systems. URIs provide a uniform way to refer to resources that may be retrievable, describable, or only conceptually identified. They are fundamental to the architecture of the World Wide Web and many networked protocols because they supply a common vocabulary for locating and referencing data, services, documents, and objects.
Structure and syntax
A URI follows a generic syntax that can include several components: a scheme (such as http, ftp, mailto, urn), an optional authority (often encompassing user information, host and port), a path, an optional query, and an optional fragment. A compact template often shown is: scheme:[//authority]path[?query][#fragment]. Special encodings such as percent-encoding are used to represent characters not allowed in some parts; internationalized domain names use additional encoding schemes (e.g., Punycode) so that Unicode can be used safely in hostnames.
Relationship to URLs and URNs
The term URI is an umbrella that covers both Uniform Resource Locators (URLs) and Uniform Resource Names (URNs). A URL provides a means to locate and retrieve a resource (for example, by specifying a network location and protocol), whereas a URN names a resource in a persistent, location-independent way. Not every URI is directly resolvable by a web browser; some URIs are purely identifiers without a defined retrieval mechanism.
Common examples of URI forms include: http://host/path?query#fragment (typical locators), mailto:[email protected] (email addresses as URIs), and urn:isbn:0451450523 (a name-style identifier). Implementations and applications interpret different schemes according to their own rules.
Standardization work for URIs is maintained in Internet standards such as RFC 3986 and related specifications produced by the IETF; these define parsing rules, normalization steps, and character handling. Because URI syntax affects linking, caching, security, and identity, proper canonicalization and careful handling of user input are important to avoid ambiguity and vulnerabilities.
For additional authoritative specifications and guidance, see Standards and further reading. Understanding URIs — their parts, allowed characters, and how they differ from simple web addresses — is essential for web developers, network engineers, and anyone working with linked data or distributed information systems.
Questions and answers
Q: What is a Uniform Resource Identifier in computing?
A: A Uniform Resource Identifier is something used to name something on the Internet.
Q: How is a URI similar to a URL?
A: URIs are similar to URLs, because they are the name of something.
Q: What kind of items can be named using URIs?
A: URIs can be used to name various items on the Internet.
Q: Can you give an example of a URI?
A: Yes, examples of URIs include various naming conventions used on the Internet.
Q: What is the significance of URIs in computing?
A: URIs are essential in computing as they provide an identifier to something on the Internet.
Q: Why are URIs important for web developers?
A: Web developers use URIs to ensure that they can name the different resources used on a website.
Q: How are URIs utilized in web coding?
A: URIs are utilized in web coding to create links to other web pages and enable identification of various elements on a website using HTML tags.
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Author
AlegsaOnline.com Uniform Resource Identifier (URI) Leandro Alegsa
URL: https://en.alegsaonline.com/art/102862