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URLs as Information

Trevor Blackman
Trevor Blackman

This guide describes the ways URLs are used to convey information about the resources they lead to, with examples and diagrams developers are familiar with.

Introduction​

URL is an acronym that stands for Uniform Resource Locator. To break down that phrase, consider each of its parts:

  • Uniform: URLs should all follow a similar pattern
  • Resource: What you get when you follow the URL, usually a file (image, video, text, etc.)
  • Locator: Tells you the location of the resource you're requesting

In its most basic form, URLs describe the location of any given file on your computer or on the internet. More or less, it's a map with directions on how to get to a file.

Local URLs​

While most computer users know about URLs on the web, many don't know that URLs are used on your computer as well. Every file on your computer has its own unique URL, whether it's a text document, a picture, a video, or anything else.

Example (Windows)​

Consider the URL below:
C:/Users/Trevor/Downloads/image.jpeg

We can represent this path as a directory tree:

C:/
└── Users/
    └── Trevor/
        ├── Desktop/
        ├── Documents/
        └── Downloads/
            └── image.jpeg

This URL is saying:

  • Starting in the C: drive, there is a folder called Users
  • In the Users folder, there is a folder called Trevor
  • In the Trevor folder, there is a folder called Downloads
  • Inside Downloads, there is a file called image.jpeg

Pretty simple, right?

Example (Mac/Linux)​

URLs on Mac and Linux start at the "root" folder /. A similar path might look like this:
/Users/Trevor/Downloads/image.jpg

/
└── Users/
    └── Trevor/
        ├── Desktop/
        ├── Documents/
        └── Downloads/
            └── image.jpg

Note: A local URL is sometimes called a "path." The above URL could be described as the "path" to access the image file.

Absolute vs Relative URLs​

Absolute URLs​

The path /Users/Trevor/Downloads/image.jpg is absolute because it starts from the root directory. It doesn’t matter where you are in the system—absolute paths always start from / (root) or a drive (C:/ on Windows).

Relative URLs​

Relative paths describe a file location relative to the current working directory. To indicate that a URL starts from the current directory, use ./.

Current Directory: /Users/Trevor

./Downloads/image.jpg
  • From /Users/Trevor, the relative URL to the image is ./Downloads/image.jpg
  • From /Users/Trevor/Downloads, the relative URL is just ./image.jpg

Traversing Parent Directories​

Relative paths can also move into a parent directory using ../. This can be repeated multiple times to move up the folder structure.

Example

Current directory: /Users/Trevor/Desktop
Desired file: /Users/Trevor/Downloads/image.jpg

Relative path: ./../Downloads/image.jpg

/Users/Trevor/
├── Desktop/   (current directory)
└── Downloads/
    └── image.jpg

Steps:

  1. Starting in Desktop
  2. ../ moves up one level → /Users/Trevor
  3. Move into Downloads/
  4. File is image.jpg

Absolute vs Relative (Comparison)​

If the file is deeply nested, relative paths can be messy:

  • Relative: ./../../../Downloads/image.jpg
  • Absolute: /Users/Trevor/Downloads/image.jpg

Most developers prefer absolute paths for clarity when files are far apart.

Web URLs​

Web URLs behave similarly to file paths but start from a domain instead of a drive or root directory.

Domain example: https://www.site.com
Everything after .com is essentially the path.

Example (Wikipedia)​

URL:
https://en.wikipedia.org/static/images/project-logos/enwiki-2x.png

Directory-like breakdown:

https://en.wikipedia.org/
└── static/
    └── images/
        └── project-logos/
            └── enwiki-2x.png

This URL is saying:

  • Start from the domain https://en.wikipedia.org
  • Go into the folder static
  • Then images
  • Then project-logos
  • Inside is the file enwiki-2x.png

Copying this URL into your browser will download or render the image.

Caveat​

The internet is a diverse ecosystem of apps written in different languages. At a fundamental level, everything above is true. However, some websites implement non-standard routing (e.g., URLs may represent database lookups, not file locations). That's a separate discussion.