An FQDN, short for fully qualified domain name, is the complete name of one specific computer or service on the internet. It names every level, from the host on the left to the domain extension on the right. In www.yourpotterystudio.co.uk, for example, www is the host and yourpotterystudio.co.uk is the domain. You'll usually be asked for this full name in a setup screen, when a certificate, a mail server or a network device needs to know which name to use.
What does FQDN mean?
FQDN stands for fully qualified domain name. A fully qualified name leaves nothing out: it runs all the way up to the root, the top level of the Domain Name System. In formal notation, the root is written as a dot at the very end. Written that way, www.yourpotterystudio.co.uk. has one more dot than the name you usually see.
Apps and everyday text often leave out that final dot, and the name is still called fully qualified. When a setup form asks for an FQDN, you can usually type it without the dot, as in mail.yourpotterystudio.co.uk.
A name that leaves levels out is partially qualified. Take blog on its own: it only makes sense once a computer knows which domain to add to it. A short name like this only works where that context is known, such as inside one network.
When you type a name into your browser, DNS looks it up to find the IP address of the server behind it. An FQDN leaves no doubt about which name to look up, because every level is already there.
The parts of an FQDN
Each part between the dots is called a label. An FQDN is written with the most specific label first and the root on the right. In www.yourpotterystudio.co.uk, the parts are:
- Hostname:
www, the label on the far left. It names one machine or service under your domain, and a hostname such asblogis also called a subdomain. - Domain name:
yourpotterystudio.co.uk, the domain you buy for your business. You choose theyourpotterystudiopart, and the extension completes it. - Domain extension:
.co.uk, the ending of your domain, like.com. If your customers are mainly in the UK, a .co.uk domain gives them an address they recognise. - Root: the top of the Domain Name System, written as the final dot after
uk.
In the extension .co.uk, the last label, .uk, is the UK's country code top-level domain, and co is the level below it.
FQDN examples
A small business often has several FQDNs under the same domain. Your pottery studio could use:
www.yourpotterystudio.co.ukfor the website your customers visit.blog.yourpotterystudio.co.ukfor a blog with news about your classes.mail.yourpotterystudio.co.ukfor a mail server that sends and receives your email.yourpotterystudio.co.ukon its own, with no hostname in front. It's fully qualified too, because it reaches the root.
All four end in the same domain, yourpotterystudio.co.uk, which you register once for your business.
Search more than 400 extensions, from .co.uk to .com, to find the right domain for your website.
Buy your domainFQDN vs hostname, domain name and URL
Hostname, domain name, FQDN and URL each name a different amount of the same web address:
| Term | What it names | Example |
|---|---|---|
| Hostname | One machine or service, by its first label | www |
| Domain name | The name you register, with its extension | yourpotterystudio.co.uk |
| FQDN | One host by its complete name, every level included | www.yourpotterystudio.co.uk |
| URL | One page or file, with the protocol and the path | https://www.yourpotterystudio.co.uk/classes |
A hostname alone tells DNS very little, because a short name like www is only understood in the context of a domain. The FQDN gives it that context by writing the hostname and the domain together. Our guide explains how a domain name works.
A URL adds more than the name: the protocol your browser uses and the path to one page. In a web address, the FQDN is the part between https:// and the path.
How to find the FQDN of your computer
- On Windows, open System Properties and look on the Computer Name tab. If the computer has joined a network domain, such as a company network, the full computer name there is the hostname plus that domain.
- On a Mac, the bottom of Sharing settings, in System Settings under General, shows your local hostname: your computer's name with
.localadded and any spaces replaced by hyphens. That name has meaning only on your local network, as with any name ending in.local. - On Linux, run
hostname --fqdnin a terminal to print the complete FQDN. The commanddnsdomainnameshows only the domain part.
On Windows, the hostname command shows only the hostname part, so use the Computer Name tab for the full name.
Frequently asked questions
What is the difference between a domain name and an FQDN?
A domain name is the name you register, such as yourpotterystudio.co.uk. An FQDN is the complete name of one host, so it usually adds a hostname in front, as in www.yourpotterystudio.co.uk. In practice, you register one domain and create the FQDNs you need under it with DNS records.
Does an FQDN include https:// or www?
An FQDN doesn't include https://, and it includes www only when the host is called www. The https:// part is the scheme, which belongs to the URL. www.yourpotterystudio.co.uk and yourpotterystudio.co.uk are different FQDNs. Type the exact one the form or service refers to.
How do I find the FQDN of my computer or server?
For a website, copy its address from your browser and remove https:// and the path after the name. What's left, such as www.yourpotterystudio.co.uk, is the FQDN of the server your browser reaches. For your own computer, the Computer Name tab on Windows or hostname --fqdn on Linux shows it.
Why does my SSL certificate or mail server ask for an FQDN?
Both need complete domain names, so a short name isn't enough. On a certificate, enter each FQDN your visitors will use, such as both www.yourpotterystudio.co.uk and yourpotterystudio.co.uk. When it sends email, a mail server gives other servers its fully qualified domain name, if it has one, such as mail.yourpotterystudio.co.uk.
Before it issues a certificate, Let's Encrypt, for example, checks that you control each name in it, so the names you enter end in a domain of your own. If you don't have one yet, register a domain for your business, then add the names you need under it, from www for your website to mail for email.
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