Someone mentions your company at a dinner. The person next to them tries to find you the next morning.
A clear, easy-to-spell domain can help them find the right website.
Start with two tests
My radio test asks whether a name conveys what the business does. My unique test asks whether it stands apart from other names. I also compare the domain with the business name and ask whether people can spell the address after hearing it.
A name rarely passes both perfectly. Descriptive names pass the radio test and struggle with the unique one. Invented names are the other way round. The ending is where you can add the meaning a name is missing.
I explain both tests, with the names I chose for my own businesses and why, in my guide to naming a company.
The endings compared
Every ending has an official record at IANA, which keeps the master list. Here is each ending’s official status, its registry and the business meaning it can carry.
| Ending | What it officially is | Run by | Business meaning |
|---|---|---|---|
| .com | Generic ending, open to anyone | VeriSign | A worldwide business. |
| .ai | Country code for Anguilla | Government of Anguilla | A product, tool or service where artificial intelligence does the work. |
| .si | Country code | ARNES (Academic and Research Network) | Super intelligence companies and products. |
| .co | Country code for Colombia | Colombia's ICT ministry (MinTIC) | |
| .io | Country code for the British Indian Ocean Territory | Internet Computer Bureau |
The ending matters because it helps identify what the business is. The separate explainers cover .com, .ai, .co and .si in more detail.
What is a .io domain?
.io is the country code for the British Indian Ocean Territory. IANA's record for .io lists it as a country-code domain, first registered in September 1997 and run by Internet Computer Bureau Limited.
Like .ai and .co, it is a country code that businesses anywhere use. As a country code, it follows its own registry's rules rather than the ICANN policies that apply to .com, so it is worth reading the .io registry's terms before you build on it.
.co vs .com
They look almost the same. .com is a generic ending run by VeriSign. .co is Colombia's country code, managed by its ICT ministry.
Both work anywhere. In my experience, .com carries the strongest sense of a worldwide business. Whichever you choose, it is worth checking who owns the other one, because some people may type it by mistake. The .co vs .com guide covers that decision in more detail.
Hyphens, numbers and spelling
Hyphens and numbers add another choice a listener must make when typing an address. Say whether a number is a digit or a word, and whether the address contains a hyphen.
Try the whole address with someone who has not seen it. Ask them to type it back, including the ending. If their spelling differs, decide whether you want to keep explaining it in conversations, adverts and email addresses. This spelling check is separate from whether the name communicates the business.
A respelling such as the Blu in BluNeural.com needs the same test. It may suit a brand, but the customer needs a clear route from hearing it to finding the exact address.
One-word and short names
One word is not always a short address. Compare its length, meaning and spelling; a familiar word may still have more than one spelling.
A word you want may already belong to someone else. Its owner sets the sale price. My guide to buying a domain that is already taken covers what that involves.
A real word on a different ending, such as .ai or .si, is one way around that. More ownable, invented names are in the brandable collection. These six single-word names are available by offer:
Before you commit to any name, check who else uses it with my name check guide. And if you want a second opinion on a shortlist, email [email protected]. Happy to help.
Common questions
What is the difference between .co and .com?
IANA records .com as a generic ending run by VeriSign, and .co as Colombia's country code, managed by its ICT ministry. Both can be used by businesses anywhere. In my experience, .com carries the strongest sense of a worldwide business.
What makes a good domain name?
The two tests I use: people understand what the business does when they hear its name, and the name is distinctive. Separately, I check its spelling and existing uses. After that, short, easy to spell and not tied to one product.
Why are one-word domains so expensive?
Short words can have several interested buyers, including large organisations. Pairing a real word with a different ending, such as .ai or .si, offers another naming option. The sale price depends on the particular domain, not just its ending.
This guide is not legal, tax or financial advice. For those questions, speak to a qualified professional where you trade.
Sources: IANA root zone database: .com; .ai; .si; .co; .io.