TLD Reference
Top-level domains: gTLDs, sTLDs and popular country codes.
Overview
The TLD Reference is a searchable directory of top-level domains — the part of a domain after the final dot. It covers generic TLDs (gTLDs like .com, .org, .net), sponsored TLDs (sTLDs like .gov, .edu, .museum) and the popular country-code TLDs (ccTLDs like .uk, .de, .jp, .io) along with the registry, purpose and any usage restrictions.
It is built for domain shoppers comparing extensions, developers configuring DNS and SEO writers looking for unusual TLDs to feature. Long-tail queries it covers include "what is the registry for .io", "is .ai a country code", "list of all gTLDs", and "TLDs with no registration restrictions".
How it works
The dataset draws from the IANA root zone database, which is the authoritative list of every active TLD. Each row carries the TLD, the registry (or sponsoring organisation), the type (gTLD, sTLD, ccTLD, brand, sponsored), a short description and a note on whether registration is open, restricted or closed.
Search runs a case-insensitive contains match across the TLD itself, the description and the registry. Typing "io" surfaces .io; typing "british" surfaces .uk via its description. The reference also flags TLDs that are widely used outside their original sponsor's intended audience — .io for tech startups, .me for personal sites and .tv for video.
Examples
.com → Verisign → gTLD, open registration, the original commercial domain
.uk → Nominet → ccTLD, United Kingdom
.io → Internet Computer Bureau → ccTLD (British Indian Ocean Territory), popular with tech
.gov → CISA → sTLD, US federal and state government only
FAQ
How many TLDs are there?
Over 1,500 active TLDs are in the root zone. The number has grown rapidly since ICANN started a new gTLD round in 2012, which added hundreds of brand and generic terms (.app, .blog, .photography).
Are .ai and .io country codes?
Yes. .ai is Anguilla and .io is the British Indian Ocean Territory. Both have become popular for tech startups because of the obvious acronym, despite their original geographic mandate.
Is .uk the same as .co.uk?
Both are managed by Nominet. .co.uk is the older commercial second-level domain; .uk is a direct registration introduced in 2014. Many businesses register both to protect their name.
Are gTLDs guaranteed to be open?
No. Many newer gTLDs are restricted to specific industries (.bank requires a banking license) or are operated as brand domains (.google is closed for Google's exclusive use).
What's a brand TLD?
A TLD applied for by a single company for its exclusive use, like .google, .ford or .apple. Brand TLDs cannot be registered by the public and are used internally for company-controlled subdomains.