URI vs URL vs URN: the main differences and why it matters

When building a website or managing online content, it’s easy to get lost in the sea of acronyms. URI, URL, and URN might seem interchangeable at first glance, but they each play a distinct role in how we identify and locate things on the internet. Understanding the difference between them can help you navigate web development with more confidence and precision.

In this article, let’s break down what each of these terms means, how they’re used, and why it all matters for your digital presence.

What is URI and what does URI stand for?

A URI, and acronym of Uniform Resource Identifier, is a sequence of characters that identify a name or a unique resource on the Internet. It contains scheme, authority, path, query, and a fragment.

URIs can be broken down into two main categories: URLs (Uniform Resource Locators) and URNs (Uniform Resource Names). Some most common URI schemes are HTTP (Hypertext transfer protocol), HTTPs, ftp, Idap, telnet, etc. Think of a URI as an umbrella term that covers both URLs and URNs. If something points to or names a resource—like a webpage, image, or document—it’s a URI. Some URIs tell you how to access that resource (like a URL), while others simply name it (like a URN). In short, all URLs and URNs are URIs, but not all URIs are URLs or URNs. XML namespace identifiers, for example, are not URLs, but they are URIs that play a key role in semantic data structures.

URL (Uniform Resource Locator) is often defined as a string of characters that is directed to an address. It is a very commonly used way to locate resources on the web. It provides a way to retrieve the presentation of the physical location by describing its network location or primary access mechanism.

A URN, on the other hand, is a type of URI that identifies a resource by its name rather than its location. URNs are used to provide a persistent and location-independent way to identify resources. For example, a URN might be used to identify a specific book in a library catalog, regardless of where the book is physically located.

What is URL & what does URL stand for?

A URL, or Uniform Resource Locator, is what you type into a browser to visit a website, view a file, or access just about anything online. It’s a specific type of URI that not only identifies a resource but tells your browser exactly how to find it.

In simple terms, a URL is like a street address for the internet. It gives your browser the directions it needs to locate and load the right content.

A URL typically consists of several parts, including the protocol (such as "http" or "https"), the domain name (such as "example.com"), and the path to the specific resource (such as "/index.html"). For example, the URL "https://www.example.com/index.html" specifies the location of the "index.html" page on the "example" website using the "https" protocol.

This tutorial tells what you need to know about URLs:

There are many types of URLs, each with its own purpose:

Canonical URLs: The preferred version of a webpage for SEO.
Callback URLs: Used in API workflows to receive responses.
Vanity URLs: Branded or shortened links, often for marketing.
Semantic URLs: Human-readable paths like /shop/mens-shoes.
Data URLs: Used to embed small files directly in HTML or CSS.

A clean URL is an HTTP or HTTPS URI that includes path information but skips the query strings and extra characters. For example:

Clean: https://www.example.com/products/shoes
Not-so-clean: https://www.example.com/products?id=123&color=blue

Clean URLs are easier to read, share, and remember. They also boost SEO performance because search engines prefer simple, descriptive paths that clearly explain what the page is about.

Some websites use protocol-relative URLs (PRLs), which omit the protocol (http: or https:) and start with //. These URLs inherit the protocol of the current page. While once popular for flexibility, HTTPS is now the default across modern web standards.

Note: The FTP protocol was once used to access files on remote servers, but modern browsers have dropped support for the FTP scheme due to security vulnerabilities.

How users interact with URLs

You may not realize it, but there are several ways to interact with or use a URL, including:

Typing the address directly into a web browser.
Clicking on hyperlinks embedded in emails, webpages, or documents.
Copying and pasting the URL into a browser or application.
Scanning QR codes that contain encoded URLs.

It’s important to note here that URLs and hyperlinks are not the same. A URL is the address of something online, like a web page or image. A hyperlink is the clickable text, button, or image that takes you there.

Absolute vs. relative URLs and URIs

An absolute URL includes the full web address—everything from the protocol to the domain and file path. For example: https://www.example.com/images/logo.png. You’ll use these when linking to something outside your site or when you need the full picture.

A relative URL, on the other hand, skips the domain and just gives the path from the current page, like images/logo.png. These are great for internal links because they’re shorter and easier to manage.

URIs work the same way. A relative URI depends on a base URI to figure out where it leads. This is very helpful for keeping your site organized, especially if you ever move things around or launch new versions of your site.

Main difference between URL and URI

The main difference between a URL and a URI is that a URL specifies the location of a resource on the internet, while a URI can be used to identify any type of resource, not just those on the internet.

URI is usually used in XML, tag library files, and other files, such as JSTL and XSTL.

URL syntax

A URL has a specific syntax, which includes the following parts:

Protocol: The protocol specifies how the resource should be accessed and is indicated at the beginning of the URL by a scheme name followed by a colon (e.g., "http:", "https:", "ftp:", etc.).
Domain name: The domain name identifies the web server on which the resource is located and is usually the second part of the URL, following the protocol.
Path: The path specifies the location of the resource on the server and is indicated after the domain name. The path can include subdirectories and the name of the resource (e.g., "/images/logo.png"). NSS – this is a namespace-specific string that identifies the internet resource. It may contain ASCII codes, digits, punctuation marks, and special characters.

URL examples

Here are some examples of URLs:

File transfer protocol (FTP) – used for a file transfer between different devices via a network. e.g. from your phone to your computer as long they are connected to the same WiFi network.

URI syntax

A URI, on the other hand, can be used to identify any type of resource, not just those on the internet. URIs can be further divided into two categories: URLs and URNs.

A URL is a type of URI that specifies the location of a resource on the internet and includes a protocol at the beginning. A URN is a type of URI that identifies a resource by its name rather than its location.

URI examples

Here are some examples of URIs:

"urn:isbn:978-3-16-148410-0" (a URN that identifies a book by its ISBN)
"mailto:info@example.com" (a URI that specifies an email address)
"tel:+1-212-555-1212" (a URI that specifies a phone number)

URI vs URL vs URN

A URI, or Uniform Resource Identifier, is a string of characters that identify a name or a resource. URIs can be used to identify any type of resource, such as a web page, an image, a video, or a specific piece of information.

A URL, or Uniform Resource Locator, is a specific type of URI that specifies the location of a resource on the internet. URLs are used to access web pages and other resources on the internet, and typically include a protocol (such as "http" or "https"), a domain name, and a path to the specific resource.

A URN, or Uniform Resource Name, is another type of URI that is used to identify a resource by its name, rather than its location. URNs are used to provide a persistent and location-independent way to identify resources.

Between a URI or a URL and their usage is essential for every webmaster. For example, building a REST API using a predictable and hierarchical structure of a URI or a URL can improve the REST API performance.

A query is an optional component that contains a query string of non-hierarchical data. It is often a string of key=value pairs. This component is preceded by a question mark.

In summary, a URI is a generic term that refers to a string of characters that identify a resource, while a URL is a specific type of URI that specifies the location of a resource on the internet. A URN is another type of URI that is used to identify a resource by its name.

What is a URN?

As mentioned above. a URN is a type of URI that identifies a resource by its name rather than its location. URNs are used to provide a persistent and location-independent way to identify resources.

For example, a URN might be used to identify a specific book in a library catalog, regardless of where the book is physically located.

The role of CDNs

A Content Delivery Network (CDN) helps load your site faster by storing copies of your content on servers around the world. When someone visits your site, the CDN sends files from the server that’s closest to them. CDNs use URIs to identify and deliver the right version of your content from different locations. The URL might look slightly different depending on where it’s served from, but it still points to the same resource. That means faster load times, smoother user experiences, and less strain on your main server.

Conclusion

At the end of the day, understanding how URIs, URLs, and URNs work behind the scenes gives you more control over how your content is structured and accessed. As you build out your digital presence, keep things simple, readable, and reliable.

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URI vs URL frequently asked questions (FAQs):

Some answers to your frequently asked questions about URI vs URL;

Should I use URL or URI?

It depends on what you are trying to do. If you are trying to access a resource on the internet, such as a web page or an image, you should use a URL. A URL is a specific type of URI that specifies the location of a resource on the internet and includes a protocol at the beginning.

If you are trying to identify a resource by its name, rather than its location, you should use a URN (Uniform Resource Name). URNs are used to provide a persistent and location-independent way to identify resources.

If you are not sure which type of URI to use, you can use a generic URI. A URI is a generic term that refers to a string of characters that identify a resource. It can be used to identify any type of resource, not just those on the internet.

How to convert URL to URI?

To convert a URL to a URI, you can simply use the URI class in the java.net package in Java. Here is an example of how to do this:

import java.net.URI;

import java.net.URISyntaxException;

public class Main {

public static void main(String[] args) throws URISyntaxException {

String urlString = "https://www.example.com/index.html";

URI uri = new URI(urlString);

System.out.println(uri);

}

This will output a URI object with the following string representation: "https://www.example.com/index.html".

You can also use the URL class in the java.net package to convert a URL to a URI. Here is an example of how to do this:

import java.net.URI;

import java.net.URL;

public class Main {

public static void main(String[] args) throws Exception {

String urlString = "https://www.example.com/index.html";

URL url = new URL(urlString);

URI uri = url.toURI();

System.out.println(uri);

}

This will also output a URI object with the string representation "https://www.example.com/index.html".

Note that both of these examples will throw a URISyntaxException if the URL string is not a valid URL. You should catch this exception or declare that your method throws it if you are using these examples in your code.

Is a URL also a URI?

Yes, a URL is a specific type of URI (Uniform Resource Identifier). A URI is a string of characters that identify a name or a resource, while a URL is a subset of URI that specifies the location of a resource on the internet.

The key difference is: all URLs are URIs, but not all URIs are URLs. URIs are a superset of URLs that can be used to identify any type of resource, not just those on the internet, while URLs are specifically used to locate resources on the internet.

For example, the following are valid URLs:

Both of these URLs are also URIs because they identify a resource (a web page or a file, respectively). However, not all URIs are URLs because they do not all specify the location of a resource on the internet.

For example, the following are valid URIs but not URLs: