URL vs. URI vs. URN - What's the Difference and Why It Matters

When working with the web or APIs, you've likely come across the terms URL, URI, and URN. While they sound similar, they serve different purposes. Here's a clear breakdown to help you understand how they differ and when to use each.

✅ What is a URL?

URL stands for Uniform Resource Locator. It's the most commonly used term and refers to the full web address you type into your browser.

• Purpose: Identifies and locates a resource on the web.
• Components: Includes the protocol (like https), domain name, path, and optional query parameters or fragment.
• Example: https://www.example.com/page?search=term#section

Key Characteristics:

• Tells you how to access a resource (via HTTP, FTP, etc.).
• Tells you where to find it.

✅ What is a URI?

URI stands for Uniform Resource Identifier. It's a broader concept that refers to any identifier of a resource, whether it shows how to find it or not.

• Includes: Both URLs and URNs.

• Example:

  • URL: https://www.example.com (this is a URI too)
  • URN: urn:isbn:0451450523 (this is also a URI)

Key Characteristics:

• General-purpose identifier.
• Can be a name, a location, or both.

✅ What is a URN?

URN stands for Uniform Resource Name. It uniquely names a resource but doesn't tell you how or where to access it.

• Purpose: Acts as a unique, permanent identifier.
• Example: urn:isbn:0451450523 – a unique ID for a book based on its ISBN.

Key Characteristics:

• Doesn't include a protocol or location.
• Useful for naming things in systems that require persistent identifiers.

🆚 Summary: Key Differences

🛠 When Should You Use Each?

• Use a URL when linking to a webpage, image, API, etc.
• Use a URI when talking about identifiers in general (common in programming, XML, and APIs).
• Use a URN when you need a long-lasting identifier (like for books, legal documents, or library resources).

🔚 Final Thoughts

Understanding the difference between URL, URI, and URN can help you communicate more clearly as a developer and avoid confusion in technical discussions. While URLs are what we use most in daily browsing, knowing how they fit into the bigger picture of URIs and URNs gives you a deeper insight into how the web works.