If you can remember your elementary school English lessons, you might recall learning how to format postal addresses so you could send a letter or navigate yourself to a particular destination.
Today, most of us navigate to Web addresses far more often than street addresses and yet we no sense about how web addresses work, what their parts mean, and how they are formatted. Here is the elementary school Internet lesson that you missed. And it is going to make you feel like an Internet Jedi.
Here is the elementary school Internet lesson that you missed. And it is going to make you feel like an Internet Jedi.
It’s easy to see the similarities between Web Addresses and postal addresses because they are both used to describe locations. However, the analogy is not perfect.
The difference between web and postal addresses is that while postal address is used to send things to a location, web addresses can be used to both send and retrieve things. Most people use web addresses to retrieve web pages, but as you will find, the syntax (the way web addresses are assembled) can have a big impact on how information is sent to, or from a location.
The “address” analogy is helpful in understanding why they are called URL’s (Uniform Resource Locators) and the “request” analogy is helpful in understanding the broader workings of the Internet. This post is all about web addresses and their components in the address sense. There are two parts: Domain Names and the URL Path. The next post will describe URL’s as dynamic requests.
Both paradigms of web addresses start at the same place: the domain. Let’s start building a web address with the domain and see how web addresses are used to locate resources on the Web.
The Domain Name
The domain name is the simplest complete form of a web address. The explanation of domains can get very complicated very quickly, but in short, the purpose of domains is mostly administrative. An organization called the Internet Corporation for Assigned Names and Numbers (ICANN) manages the registration and use of different domains. This prevents the Web from becoming one giant mess of conflicting web address. See: “namespaces.”
A good analogy for Web domains is telephone numbers. A complete phone number starts with a country code, (1 for the US) and is then followed by an area code (e.g., 415 for San Francisco), another three numbers that belong to a smaller area and ends with a four digit line number.
Domain names work similarly in that each domain belongs to another domain and may have domains within it. Domains are read from right to left and separated by periods. The “highest level” domain is on the right side of the domain called the top-level domain (TLD). In the example, above the TLD is .com.
The Top Level Domain (TLD) is the extension after the final “.” in a domain name. For example, “com” is the TLD for “trevorfox.com.”
From right to left, each domain after the TLD is a subdomain of the previous domain. This means www.example.com domain is a subdomain of the example.com domain. Likewise, for the domain www.bbc.co.uk, www.bbc.co is a subdomain of the TLD .uk.
Now let’s get technical…
Domain names on the Internet correspond to one or more IP (Internet Protocol) addresses of a server that host the content of that domain. (This is why domains names are also often referred to as hostnames.)
IP addresses and the system that translates domain names to IP addresses (called the Domain Name System, or DNS) are bits of Internet magic, and most people don’t need to understand how they work. But it ‘s good to know that every domain on the web can also be reached directly through that domain’s IP address. For example, the range IP addresses for Facebook starts with 173.252.91.
A last interesting tidbit is that your computer has its own IP address which allows it to send and receive things to and from other IP addresses.
What you must know about the Domain Name:
- Domain names are read from right to left, with the Top Level Domain (TLD) at the far right. Every domain to the left of the TLD is a subdomain of the one to it’s right.
- The domain name or hostname is the human readable “Internet address” of a server.
- Every domain corresponds to at least one IP (Internet Protocol) address.
The Path (aka “the slashes”)
To understand the path, it is easiest to think of web addresses as URL’s (Uniform Resource Locators). In the simplest sense, a URL path represents the location of “resource” on a web server. A resource could be any type of file, but for most of us, URLs are used in our web browsers to retrieve HTML pages, images (e.g., .jpg or .png), and PDFs, from web servers.
Any type of file, but for most of us, URLs are used in our web browsers to retrieve HTML pages, images (e.g., .jpg or .png), and PDFs, from web servers.
In this way, web servers are much like the computers you use: files are stored in directories, (we call these folders on our personal computers) and these directories are organized in a “nested” structure. Nesting means that directories can contain subdirectories which can contain subdirectories in the same way you can place file folders within other file folders.
The URL path represents directories as a sequence of directory names separated by slashes. The directory names are read from left to right and each directory contains the directory to its right. After the slash at the far right of the path is the file name. File names often (but don’t have to) have the file extension (e.g., .html) attached to them.
You may notice some websites name their directories in a way that is easy for humans to read and understand. This practice is called semantic URL’s, meaning they can be understood almost like human language. Ecommerce websites often use semantic URLs to convey the organization of their product catalog.
An example of semantic URLs would be https://www.workers-supply.com/tote-bags/craftsman-tote-bag where the Craftsman Tote Bag is a member of the Tote Bags collection.*
Semantic URL’s are good for Search Engine Optimization (SEO) and User Experience (UX). This makes navigating up the product hierarchy as easy as removing directories from the end of the URL path. To use the previous example, https://www.workers-supply.com/tote-bags/ would take you to the whole Tote Bags collection.
*This example also shows that files are not required to have file extensions attached to them. craftsman-tote-bag is the name of an HTML file that is retrieved but does not have the .html file extension attached.
What you must know about the URL Path:
- Web Addresses are synonymous with URL’s (Uniform Resource Locators)
- The URL path represents the location of files within the directories of a Web server
- Directories can contain multiple directories and/or files. Directories within other directories are called subdirectories of the parent directory.
- Semantic URL’s use human-readable naming conventions to clearly present the organization of directories and location of files
Up Next: Dynamic URL’s and Requests
As I mentioned before, there are two ways to think about Web Addresses: as locales (nouns), and as requests (verbs).
Now that the foundation is laid for URL’s as location identifiers, the next post will explain something we humans largely take for granted: how Web servers create dynamic Web pages from dynamic URL’s. Google and the flight search engine SkyScanner are perfect examples of this and will be the examples for this next segment. And trust me, you will never look at a URL the same way again.
Sign up to learn more about the Web!