Mash's Musings

How to read a URL

Published Sep. 11, 2022

I recently read a funny blog post on things learned way too late in life. While there are certainly no shortage of such things to share, I have found some of my biggest "woah" moments in the last few years to be in the world of computers. Being pretty new to the field and largely self-taught, I consistently have the bittersweet experience of noticing a glaring blindspot and the lightbulb moment once the gap is filled in.

One of these unintuitive blind spots for me had to do with reading URLs. As an example, let's take the URL of this web page as an example:

If you are at all literate in English, you tend to read from left to right. Thus, I would have interpreted the URL as, "Some mumbo-jumbo colon-slash-slash, then the mashsmusings site which has something to do with the org neocities, then reading a specific post within 'posts'." While the left-to-right heuristic is great 99% of time, it unfortunately doesn't work when reading your favorite waifu manga and, confusingly, only mostly works for reading URLs. To see what I mean, let's dig into the different components of our URL.
   1                2                3             4
  1. protocol: This part is kind of complicated but, in short, this defines what set of instructions needs to be used to read the resource. This will almost always be Hypertext Transfer Protocol to read from web servers but sometimes you might run into something like "mailto:" which initiates an email message to a specific email address.
  2. domain: The domain can be thought of as the human-readable name of a server, AKA someone else's computer. Confusingly, domain names are interpreted in reverse order and in hierarchical fashion. So in our example, our top-level domain (TLD) is "org", "neocities" is a single subdomain under "org", and "mashsmusings" is a single subdomain under "neocities". This backwards-reading domain tells us which computer on the internet we're interacting with.
  3. path name: The series of folders you can imagine clicking through on the server's hard drive. In our example, this is the "/posts" directory under the root directory.
  4. file name: The name of the actual file you are requesting from the server in the directory specified by the path name beforehand, including the extension associated with that file. This is usually a ".html" file specifying a web page but sometimes it can be a .jpg or .mp4 for an image or video clip respectively.

Putting this all together gives a more illuminating interpretation than the one prior. Now the same URL can be interpreted as "Using the HTTPS protocol, go to the server registered as 'mashsmusings', a subdomain of 'neocities', a subdomain of 'org'; go to the posts folder, and get me the file called 'how-to-read-a-url.html'". Despite being an avid internet user since age 7, I never picked this up until I had to set up my own site — the more you know!

As a side note, learning about domain hierarchies being read right to left, made me wonder why most sites have the terminal subdomain "www". Turns out, it's completely pointless! Having a "www" subdomain was a legacy convention to specifying that your server was on the Worldwide web but over time, that convention has fallen away in favor of clearer, more concise domain names. Not everything has a good reason.