The extension is the part after the dot, and there are well over a thousand of them. Most of the choice is marketing; a few genuine differences matter, and they are worth knowing before you commit a business name to something.
What actually differs between extensions
Price, and specifically renewal price. Some extensions register cheaply and renew at several times that. The renewal figure is the one you will pay every year afterwards.
Eligibility rules. Many country extensions require a local presence, a registered company, or a specific connection to the country. These are registry policies and no registrar can waive them.
Whether privacy is allowed. Several registries require genuine public contact details. If WHOIS privacy matters to you, check before registering. For that, see WHOIS privacy protection.
Transfer and renewal mechanics. Some country extensions have their own transfer process that does not use the standard EPP code system.
What does not differ
Search ranking. A .com does not rank better than a .shop or a .io because of its extension. This claim persists in SEO advice and there is nothing behind it.
Technical function. Every extension resolves the same way, holds the same record types, and works identically with hosting and email.
Security. No extension is inherently safer. Certificates work the same on all of them.
The reason .com still wins
Not ranking. Recall.
People type .com by default, assume it when half-remembering a name, and hear it as the neutral option when a domain is read aloud. That is a real advantage, and it is the whole of the advantage.
If the .com is available and affordable, take it. If it is not, the alternatives below are genuinely fine, and considerably better than an awkward .com with hyphens or a misspelling.
The categories worth knowing
The originals. .com, .net, .org. Universally understood, no eligibility rules. .org carries a non-profit association that is convention instead of a requirement.
Country codes. .co.uk, .de, .com.tr and so on. Strong signal for a local business and often the first choice in their market. Many carry eligibility rules; check before planning around one.
Newer generic extensions. .shop, .app, .dev, .io and hundreds more. Availability is much better, and a good short name on one of these beats a poor name on .com.
Two practical notes on this group: renewal prices vary enormously, and .app and .dev enforce HTTPS at the browser level, which is fine, since Ahosting includes free SSL, but it means plain HTTP will not work at all.
Registering several
Common advice is to register variations defensively. Worth being realistic about it.
Registering the .com and your country extension is reasonable for a business with a name worth protecting. Registering fifteen variations is a recurring annual cost against a threat that mostly does not materialise.
If you do register several, point them all at the main one with a redirect rather than letting them sit empty. Domain forwarding walks through doing it properly. And remember every one of them renews annually.
Choosing the name itself
Shorter is better, mostly because it survives being said out loud.
Avoid hyphens and numbers. Both fail the telephone test: "is that with a dash?" and "the number four or f-o-u-r?" are questions you will answer for years.
Check how it reads run together, which is how it appears in a URL. Some perfectly reasonable word pairs produce an unfortunate third word, and it is better to notice that now.
Before you commit
Check the renewal price, not just the registration price. Check the eligibility rules if it is a country extension. And check the name is not an existing trademark in your field, because a domain does not grant any right to use a name someone else holds.
None of these can be changed afterwards. Moving a name to a different extension is a new registration and a full migration, not a setting. Registering a domain explains the ordering steps once you have decided.
A previously used name in the extension you wanted carries history that is not visible from the name. How to Buy an Aftermarket or Expired Domain Safely deals with the checks.
Check the name is free everywhere it matters
A domain being available is one of several checks, and the others are cheaper to do now than to discover later.
Search the trademark registers for the countries you will trade in. Check the social handles you would want. And search the name as a phrase to see what already ranks for it, since competing with an established meaning is a long project.
whois example.com | head -5 dig example.com A +short dig example.com MX +short
A name that is registered but shows no site and no mail may be available to buy. One with records pointing at a live service is in use, whatever the site looks like.
Doing all of this takes twenty minutes and prevents the expensive version, which is renaming a business after it has printed anything. Choosing a good domain name goes into the name itself.
Some extensions carry obligations
Not every extension is available to everyone, and the conditions attach to the registration rather than to the use.
Country extensions frequently require a local presence, a local address, or a registered company in that country. Some restricted extensions require membership of a profession or an industry, and verification can be requested after registration rather than during it.
The consequence of failing a later check is losing the name, not a warning. That is a poor outcome for a domain a business has built on, and it is entirely avoidable by reading the eligibility rules before registering rather than after.
Renewal pricing is worth the same attention, since some extensions renew at several times the first year price and the difference compounds across a portfolio.
Do not let the extension become a redirect you forgot
Registering variants defensively is reasonable. Leaving them unconfigured is how they become a liability.
for d in example.net example.org example.co; do
printf '%-16s %s\n' "$d" "$(curl -s -o /dev/null -w '%{http_code} -> %{redirect_url}' "http://$d/")"
done
Each should redirect to the main name in a single hop, and each needs its own certificate if the secure form is to work without a warning.
An unconfigured variant serves nothing, or worse serves a default page from the host. Both are a name carrying your brand and showing something you did not write. Parking or holding a domain covers the arrangement.