.io is the country-code TLD for the British Indian Ocean Territory, but in practice it is the default "we are a tech startup" signal on the internet. Since around 2012, .io has been the most popular alternative to .com for software companies, and that pattern only intensified with the AI wave.

What makes .io popular

Two things. First, semantic overlap with I/O — input/output — which reads as "this thing handles data". Second, scarcity of clean .com names pushes founders to grab the .io equivalent before someone else does. The result is a market where .io signals technology even more loudly than .com in some niches.

Pricing and registration

Typical registration is $30–$60 per year, more expensive than .dev or .co.
No restrictions on who can register; .io is open to anyone globally.
Short dictionary words are almost entirely aftermarket — expect four-figure USD pricing for one-word names.
Registration sites like Porkbun, Cloudflare, and Namecheap offer WHOIS privacy at no extra cost.

Common pitfalls

Premature renewal spikes: some registrars run $0.99 first-year offers that jump to $80+ on renewal. Always check the renewal price.
Trademark issues: .io has no special dispute resolution protections beyond UDRP, so short names are frequently parked.
Sovereignty risk: the UK's long-term status of the territory has historically prompted speculative "what if .io goes away" threads. So far ICANN has protected ccTLD continuity, and there is no concrete plan to retire .io.

Who should use .io

Tech startups, especially B2B SaaS.
AI products where .ai is too crowded or too expensive.
Open source projects that want a "Tools company" vibe.
Products whose identity leans on data pipelines and APIs.

When to pick .dev or .ai instead

For developer tools, .dev reads more credibly to engineers and costs less. For AI-native products, .ai is the strongest signal — but at $60–$150/year, with limited availability, many early-stage founders still pick .io as a realistic middle ground. Read our best TLDs for developers overview for a side-by-side.

Checking .io availability with namebox.dev

namebox.dev checks .io against the registry in real time through RDAP (RFC 7483). Each name displayed as available has been verified against the authoritative registry at the moment of your search — not against a stale DNS cache. Run a search and filter for .io candidates.