Nomenclature of a URL

I was asked recently for some advice on how to migrate a domain. A migration is effectively taking all the files that display your website and moving them from one place to another. Often the reason for doing this is to move hosting providers or a transition from a development to a live phase (publishing to give it the traditional term).

In this conversation, I was explaining the nomenclature of a URL — the different parts of the website address and what they mean or do and I thought it would be useful for other people to attempt to explain it here in case you’re looking at migrating a website. So here goes.


The protocol is the first part of the address and defines whether your site is secure or not. http and https can both be used, however search engines such as Google will often penalise websites that don’t use the https protocol and so deny you the little padlock that appears in the browser. The worst-case scenario is that some visitors could get an unsafe message in their browser. The colon and two forward slashes are both parts of the protocol.


The hostname is a part of the address that proceeds your domain name and is not mandatory in the browser. This means with some websites you won’t see the www bit of the address. In the early life of the internet, it was essential to tell the computer and related network what type of host you were trying to access. Now a web server, which is what this particular hostname specifies, is more common.


A domain name is the part of the address that is obviously the bit you can customise and is unique to your product, brand or organisation. No two domains (provided they use the same top-level domain) can be the same. This means it is getting harder to find domains that haven’t already been registered. According to the latest figure from last year, there are 360 million registered domains worldwide.

Top-level domain or TLD

Also known as domain extensions they are used to help define the location of a website. For instance .com historically was associated with websites registered in the US. It’s much less relevant now considering there are over 1,500 domain name extensions and you can register what you like from wherever. Essentially domain registrars are running out of unique domain names to sell, hence adding more domain extension options.


The directory is a tricky one, essentially this part of the address by definition could be a directory, folder, category, tag, slug or many other things. It depends on the technology you are using to create your website as to what this might be.


The file is a bit easier as it is the only part of the address that does the exciting bit for web designers — displaying the lovingly crafted website that we spend hours building.


Finally, and again not a mandatory part of the address is the file extension. Modern browsers are much cleverer at working out what to load for themselves so you won’t always see this in the address. If it is there it’s often a clue to the type of technology used to build the site. I’ve written an article called What should I use to build a website? that helps define some of these.

So next time you visit a website, once the page has loaded, look at the address or click in the bar, and see if you have some of these parts. Hopefully, you’ll understand a little more about what they do.