URI vs URL: Key differences explained

A URI, or Uniform Resource Identifier, is a way to identify any resource online, such as a webpage, a document, an image, or something else entirely. Think of it as a unique ID. This identification can be based on the resource’s name, its location, or both.

A URL, or Uniform Resource Locator, is a specific kind of URI. It identifies a resource and also tells you exactly where to find it and how to get there. It includes the access method, like https:// and the address of the resource on the web, like www.example.com/page.

Here’s a quick breakdown of the main differences.

Category	URI (Uniform Resource Identifier)	URL (Uniform Resource Locator)
Purpose	To identify a resource by name, location, or both.	To locate a resource by specifying its access method and location.
Relationship	The superset of a URN and a URL.	The subset of URI.
Syntax	Contains components like a scheme, authority, path, and query.	Has similar components to a URI. Its authority consists of a domain name and a port.
Example	ISBN 0-476-35557-4	https://hostinger.com
Common use cases	Usually used in XML, tag library files, and other files, such as JSTL and XSTL.	Mainly used to search web pages on the internet.
Scheme definition	URI scheme can be a protocol, a specification, or a designation like HTTP, file, or data.	URL scheme is a protocol, such as HTTP and HTTPS.

The key distinction is that every URL is a type of URI, but not every URI is a URL.

Think of it like this:

• A URL is like their complete home address – it tells you exactly where to locate them.
• A URI is like a person’s name – it identifies them.

Key differences between URI and URL

The main difference is that a URL specifies the protocol and the location of a resource, whereas a URI can identify a resource by name, location, or both.

Here’s a breakdown of what that means in practice:

• Scope: A URI is the parent category, representing the broadest term for any resource identifier. A URL is a specific kind of URI, making it a subset with a narrower focus.
• Purpose: A URI’s main purpose is to identify a resource with a unique name. Basically, it tells you what something is. A URL’s purpose is to locate a resource by providing a web address – it tells you where to find it.
• Syntax: A URI can have a flexible syntax. Its scheme can be a name (urn:), a protocol (https:), or another specifier. A URL has a stricter syntax that must include an access protocol like https or ftp.
• Usage: URIs are often used in technical contexts like data schemas, such as XML, to give something a unique ID. URLs are used every day to access links, websites, and other resources in a web browser.
• Example: A URI can be an identifier like urn:isbn:978-0321765723, which names a specific book but doesn’t tell you where it is. A URL is a full address like https://www.hostinger.com/tutorials.

Syntax comparison: URI vs URL

While both share a common structure, a URL has stricter syntax rules and must contain specific components to be valid.

Here’s how the syntax compares:

Scheme

This is the first part of the address that ends with a colon, like https: or mailto:. It tells the computer what it’s dealing with.

• In a URL, the scheme is an instruction, like https:, which tells your browser to fetch a webpage securely.
• In a URI, it can be more abstract. For example, urn:isbn:0451450523 just names a book without telling you where to find it.

Authority

This is the part right after the // that usually contains the website’s domain name, like www.hostinger.com.

• For URLs that point to websites, the authority is how you know which server to connect to.
• For some URIs, this part isn’t needed. An email link like mailto:example@email.com works perfectly fine without it.

Path

This part comes after the domain and looks like a folder path on your computer, such as /tutorials/uri-vs-url. It pinpoints the exact page or file you want on that website.

Query

This optional component starts with a ? and is used to send extra information, like ?search=how-to-build-a-website. Think of it as adding a filter to your request.

Fragment

This is an optional part that begins with a #, like #section-2. It tells your browser to jump directly to a specific part of the webpage, so you don’t have to scroll to find it.

When to use URI vs URL

Knowing when to use each term depends on what you’re trying to accomplish.

Use a URL when you need to access a resource on the web. This is the most common use case.

If you’re putting an address in a browser, linking to a page in your HTML, or calling an API endpoint, you’re using a URL. It provides the complete address needed to retrieve something.

Use a URI when you need to uniquely identify a resource, regardless of its location. This is more common in technical contexts.

For example, in XML or RDF files, a URI can act as a unique name for a data element or concept. Instead of pointing to a webpage, it just needs to be a unique identifier.

Real-world use cases of URI and URL

Let’s look at how URIs and URLs are applied in different scenarios to make the distinction clearer.

URI use cases

Naming resources

URIs are used to assign unique serial numbers to creative works. This allows them to be identified in databases and catalogs without pointing to a specific file online.

For example, an ISBN (International Standard Book Number), like urn:isbn:978-0321765723, uniquely identifies a specific book but doesn’t tell you where to find it online.

Similarly, an ISAN (International Standard Audiovisual Number), like urn:isan:0000-0004-87D7-0000-Q-0000-0000-6 can identify a movie without providing a link to watch it.

Identifying telephone numbers

The tel: scheme creates a URI that identifies a telephone number.

For example, tel:+1-816-555-6666 is a globally unique identifier for a phone number. It doesn’t refer to a physical device but simply names the resource.

URL use cases

Web Pages

This is the most common use case. When you type an address into your browser or click a link, you’re using a URL to navigate the internet.

These are often absolute URLs, containing the full protocol, domain, and path, like https://www.hostinger.com/tutorials/uri-vs-url.

Internal pages

URLs can also appear without a protocol and domain, specifying only the path. Known as relative URLs, they link to a file within the same website.

For example, the relative URL for the page above would simply be /tutorials/uri-vs-url.

REST APIs

In API development, endpoints are represented by URLs. For instance, https://api.example.com/users/123 is a URL that allows an application to interact with the data for user 123.

Search engine optimization (SEO)

Search engines like Google crawl and index URLs to understand a website’s structure and content. Clean, descriptive URLs are a best practice for helping both users and search engines.

Email addresses

A URL can specify an email address using the mailto: scheme, such as mailto:abc@example.com. Clicking this link on a webpage typically opens your default email client.

Redirects

URLs are crucial for redirecting users from an old page to a new one. For example, if a blog moves from blog.example.com to example.com/blog, a redirect ensures that users accessing the old URL are automatically sent to the new location, preventing 404 errors.

Remote Access

URLs can use protocols other than HTTP. For example, the telnet://192.0.2.16:80/ URL is used to connect to a remote computer at a specific IP address and port, often for troubleshooting servers.

How are URIs and URLs related?

The relationship between URI and URL is hierarchical. URI is the parent category, and URL is one type of URI.

Think of it like this:

• URI (Identifier) is like the concept of a person’s identity.
• A URL (Locator) is like a person’s home address. It tells you where to find them.
• A URN (Name) is like a person’s unique national ID number. It identifies them but doesn’t say where they live.

Both a home address and an ID number are forms of identification, but they serve different functions. Every URL provides a location, making it an identifier. But not every identifier provides a location.

Should I use URL or URI?

It all depends on what you’re trying to do. If you’re linking to a webpage, a stylesheet, or an image online, you’re using a URL.

If you’re a developer defining a unique identifier for a piece of data in a schema that won’t be accessed over the web, you’re using a URI.

In practice, unless you’re a developer, a URL is what you will use for almost everything you do online. It’s the locator for all the resources we need when browsing websites or developing them.

The heart of every URL is its domain name. To get the full picture, check out our guide on what a domain name is and how to choose the perfect one.

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