components of the url



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Naming is hard. Recently, I was working on constructing a URL to send users to when I realized that I didn’t actually know the parts of the URL I was constructing.

For example, I was refering to everything before the path of a URL as the baseURL. Figuring that wasn’t exactly correct (turns out host is what I was looking for), I did some digging. Below is what I found about the different components of the URL.

Basics Of The URL

There are four parts to a URL (Uniform Resource Locator):

  1. Scheme
  2. Host
  3. Paths
  4. Query strings are preceded by a ? and separated by & characters

The scheme (also called a protocol) includes: http, https, and ftp

The host is made up of several parts:

  1. The TLD or top level domain (e.g., .com, .net, etc.)
  2. The domain the example in
  3. (Optionally) a subdomain, such as blog in

Interestingly, the host has a directory equivalent. Using our blog example, this resource would be located at com/example/blog.

These parts come together in the following way:


The path is also the name of the resource being loaded. Paths begin with a single /. If there is no trailing slash, it means we’re loading the root resource, often (always?) the index file in the directory.

Not all resources are nameless, however. For example, if you wanted to have a blog path (instead of a subdomain), you could load it at

Lastly, there’s the query string. Query strings are made up of three parts:

  1. The initial indicator, marked by an ? following a path
  2. A key value pair
  3. Subsequent separator, marked by the &.

For example

Putting It Into Practice

So, how do we use this information?

Well, we can access it with the API for Location which is available on both the window and document.

It’s important to reference the documentation however to understand the difference between the host and the hostname (the former is the latter with the specified port, if it exists).

For example, this section’s Location is:

const location = window.location
// location = {
//   origin: ''
//   protocol: 'https:'
//   host: ''
//   hostname: ''
//   port: ''
//   pathname: '/blog/2020-03-02/url-components/'
//   search: ''
//   hash: '#putting-it-into-practice'
//   href: ''
// }

And when running it locally:

// location = {
//   origin: 'http://localhost:8000'
//   protocol: 'http:'
//   host: 'localhost:8000'
//   hostname: 'localhost'
//   port: '8000'
//   pathname: '/blog/2020-03-02/url-components/'
//   search: ''
//   hash: '#putting-it-into-practice'
//   href: 'http://localhost:8000/blog/2020-03-02/url-components/#putting-it-into-practice'
// }

While not immediately obvious, the query string would live in the search property.

Location Methods

There are also some useful methods in the location API.

For example location.assign and location.replace. Note, the biggest difference is the behavior with history (assign adds to the browser history, replace does not.)

The difference from the assign() method is that after using replace() the current page will not be saved in session history, meaning the user won’t be able to use the Back button to navigate to it.

If looking to redirect a user, you can also use the


Hi there and thanks for reading! My name's Stephen. I live in Chicago with my wife, Kate, and dog, Finn. Want more? See about and get in touch!