The country-code top-level domain assigned to the British Indian Ocean Territory is .io.
The two-letter label comes from “Indian Ocean,” while the formal country-code assignment corresponds to the territory’s ISO 3166 code, IOT. IANA delegated .io in 1997, and it remains listed as a country-code top-level domain in the DNS root. Internet Computer Bureau Limited manages the registry.
Unlike many territory-linked domains, .io registrations are widely available internationally rather than being limited to residents of the British Indian Ocean Territory. That openness helped make the domain popular with technology startups, software projects, browser games, and services that interpret “IO” as input/output.
A common mix-up is treating .io as a generic technology domain. Its popularity is commercial and cultural, but its technical classification is still a ccTLD. It is also distinct from .bo for Bolivia, .bt for Bhutan, and .bi for Burundi. Political changes involving the Chagos Archipelago have prompted discussion about the domain’s long-term future, but .io remains the assigned and operating code in the current DNS root.