.com vs .io vs .co vs .ai: Choosing a Domain Extension

Two kinds of ending

Every domain ends in a top-level domain, and IANA, which keeps the root of the domain name system, lists each one in its Root Zone Database with a type and a manager. The two types that matter for a website are generic and country code. A generic ending such as .com or .org is run by a registry company. A country-code ending is the two-letter code of a country or territory, and in the records below its manager is often a government body. How the whole system fits together, from registrar to DNS to hosting, is covered in domain, DNS and hosting explained.

So .io, .co, .ai, .me and .tv are all country codes. They became popular because the letters spell something useful in English, not because the sites are based there.

How Google reads them

For search, the type matters less than you might expect. Google Search Central says a country-code domain gives "a strong signal" that a site is meant for that country, and that generic domains are not tied to a location. But it also keeps a list of country codes it treats as generic, because they are widely used as vanity endings:

.ad .ai .as .bz .cc .cd .co .dj .fm .io .la .me .ms .nu .sc .sr .su .tv .tk .ws

That is 20 endings, and every country code in the table above is on it: .io, .co, .ai, .me, .tv. A site on .io or .ai is treated like a .com site; it is not shown preferentially to people in the British Indian Ocean Territory or Anguilla. Google notes that the list may change. A country code that is not on it, such as .de, .fr or .ca, does tie the site to that country, which is what you want for a local business there and not what you want for a site aimed at the whole world.

For the trade-offs of putting regional versions on separate domains, subdomains or folders, see subdomain vs subdirectory.

The registry sets the rules

Each ending has its own registry policy for who may register, what it costs and how disputes are handled. Google warns that some countries restrict who can register their country code, so check before you plan a site around one. The IANA records also show that managers change: the .co record lists a redelegation to .CO Internet SAS in 2009 and a transfer to the Colombian ministry, MinTIC, in 2020.

Practical consequences:

• Read the registry's policy. Each IANA record names the registry's website. Prices, renewal terms and eligibility live there.
• Compare renewal prices. Look at what year two and later cost, not only the first year, before you print the address on anything.
• Know the expiry. A lapsed domain can be lost. The what happens when a domain expires guide walks through the stages.

An ending with a technical rule: .app

Some endings come with a technical condition. The .app registry states that the whole ending is on the HSTS preload list, which makes HTTPS required on all connections to .app websites, with no setup on your side. Browsers will not load a .app site over plain HTTP at all. That is good for security and a trap if you planned to start without a certificate. The HTTP vs HTTPS guide explains what HTTPS adds and what a certificate is for.

Length and saying it aloud

The ending is part of what people type and say. For one name, the full address grows with the ending:

Shorter is easier, but say it aloud too. ".co" heard over the phone can be written down as ".com", so a .co site risks sending visitors to whoever owns the .com. If you take a .co, try to own the .com as well and redirect it.

Choosing, step by step

1. Start with the name. The domain name generator combines your keywords with prefixes, suffixes and short forms across several endings, so you see which names are still free.
2. Prefer .com if it is free. It is generic, not tied to any country in search, and avoids the .co and .com mix-up.
3. If .com is taken, look it up. The WHOIS lookup shows the registrar, creation and expiry dates and status. A parked domain registered last month is a different situation from a company that has used it for 20 years.
4. Pick a country code only on purpose. For a business in one country, its code is the natural choice and a strong local signal. For a global product, .io, .co and .ai behave like generic endings in Google Search, but remember who runs them.
5. Check the registry's rules and renewal price before you commit, and set the domain to renew automatically.
6. Register the obvious variants that you can afford and redirect them, so typos and the .com do not lead somewhere else.

Frequently asked questions

Sources

• IANA Root Zone Database (the list of top-level domains and their types: generic, country code, special use, test)
• IANA: Delegation record for .io (country code, manager Internet Computer Bureau Limited, address in Diego Garcia, British Indian Ocean Territory)
• IANA: Delegation record for .co (country code, manager MinTIC in Bogotá, technical contact CentralNic, redelegation 2009 and transfer 2020)
• IANA: Delegation record for .ai (country code, Government of Anguilla)
• IANA: Delegation records for .com and .net (generic, VeriSign), .org (generic, Public Interest Registry), .app (generic, Charleston Road Registry), .me (Government of Montenegro) and .tv (Tuvalu)
• Google Search Central: Managing multi-regional and multilingual sites (ccTLDs are a strong country signal, pros and cons, some countries restrict registration, gTLDs not tied to a location, the list of ccTLDs treated as generic)
• Google Registry: .app (the TLD is on the HSTS preload list, so HTTPS is required on all connections)

Written by Tobias. Updated October 30, 2026.