.si Domain for Super Intelligence: The Complete Guide

What is a .si domain?

.si is the country-code top-level domain (ccTLD) for Slovenia, the small EU country between Italy, Austria, Hungary and Croatia. Like every two-letter extension, it comes from the international ISO list of country codes, and it has existed since 1992. If you want the background on how extensions are organised, what is a TLD? covers generic domains, country codes and the newer extensions.

Who runs .si

The .si registry is Register.si, operated by ARNES, the Academic and Research Network of Slovenia. The registry keeps the master list of every .si name and sets the extension's rules, while you buy the domain through an accredited registrar, exactly as you would a .com. For years almost all .si registrations came from Slovenian businesses and individuals.

How a country code becomes a tech brand

This isn't the first time letters have mattered more than geography. .io (British Indian Ocean Territory) was adopted by developers because it reads as input/output. .ai (Anguilla) became the home of artificial intelligence. .tv (Tuvalu) became the extension for video and streaming. .si is following the same path: the domain hasn't changed, but what people read into the letters has.

Why .si became the super intelligence domain

"Super intelligence" describes AI that goes beyond human-level ability across the board (SI vs AI explains both meanings of the term). It's been a research and investment buzzword for a while, but in September 2026 the term went mainstream after the US government began promoting "Super Intelligence" and "SI" as its preferred name for advanced AI, according to widespread press coverage. Almost immediately, people noticed that .si was a real, registrable domain extension.

The registration rush

The response was dramatic. Press reports citing the Slovenian registry put new .si registrations at more than 46,000 in September 2026, against roughly 3,500 in August, an increase of well over ten times in a single month, and the total number of .si domains passed 200,000 for the first time. Registrars reported that most orders were new registrations rather than transfers, a sign of fresh demand rather than existing owners moving around.

Who is buying .si names

• AI startups registering their brand on .si next to their .ai or .com, to launch on it or simply to keep it out of anyone else's hands.
• Established AI companies making defensive registrations so nobody can build a lookalike site on their name. The SpaceXSI rebrand made this very public: see will SpaceX buy spacex.si? for who holds the Musk-related .si names.
• Domain investors buying short words and AI terms in the hope of reselling them, the same pattern seen with .ai.
• Slovenian businesses, the extension's original users, who now find their own country code competitive.

.si vs .ai: which should you choose?

If you're naming an AI product, the real comparison is .si against .ai, with .com and .io as the safe alternatives.

When .si is the better pick

• Your product or company is explicitly about super intelligence, reasoning or next-generation AI.
• The .ai of your name is taken or priced as a premium, but the .si is free.
• You want a short, memorable name at a normal domain price.
• You're early-stage and happy to bet on the term taking off.

When .ai (or .com) is still safer

• You need instant recognition with customers, investors or press today.
• Most of your traffic will come from Google outside Slovenia (see the SEO section below).
• AI is a feature of your product, not the whole story; a neutral .com ages better.

Most founders don't have to choose. A standard .si costs far less than a .ai, so registering both and redirecting one to the other is cheap insurance. Check the pair together on the .si domain checker, which shows the .ai, .com and .io next to the .si, or read our full guide to .ai domain names.

How much does a .si domain cost?

A standard .si domain is priced like a mainstream country code, not like .ai. At the time of writing, registrars list .si at roughly $12 to $30 a year, with renewal prices in the same range. That's a fraction of the typical .ai price, which is one reason .si has been so easy for founders to add to their portfolio.

What changes the price

• Registrar: each registrar sets its own retail price and renewal price, so compare both before you buy.
• Term: .si can usually be registered for one year or several years at a time.
• Aftermarket names: short words that investors registered early in the rush are being resold, sometimes for thousands. One AI company reportedly paid $20,000 for a single-word .si before the boom.
• Extras: WHOIS privacy, email and hosting are separate costs, as with any domain.

For a wider look at how domain pricing works, including first-year deals and renewals, see how much does a domain name cost?.

Does a .si domain hurt SEO?

A .si domain won't stop your site ranking, but there's one real difference from .ai that you should know about before building a global brand on it.

Generic vs country-targeted

Google keeps a short list of country codes it treats as generic, because they're used worldwide for reasons unrelated to the country: .ai, .io, .co, .me and .tv are on it. At the time of writing, .si is not. That means Google treats a .si site as associated with Slovenia by default, which can help in Slovenian results and make it harder to rank in other countries.

How to rank a .si site internationally

• Write for your real audience: clear English (or local-language) content signals who the site is for.
• Earn links from your market: links from sites in the countries you target matter more than the extension.
• Use hreflang if you publish several language or country versions.
• Consider a generic main domain: run the main site on a .com or .ai and redirect the .si to it, at least until Google's view of .si changes.

How to find a .si domain that's still available

The obvious single words went in the first few weeks of the rush, but there are still plenty of good .si names if you search methodically.

1. Brainstorm names. Start with our 120 super intelligence company name ideas. The AI startup name generator turns a keyword into 20 AI-style ideas; the domain name generator adds brandable combinations.
2. Check your favourite on the .si domain checker. It shows the .si first, then the same name on .ai, .com, .io, .app and .dev.
3. Compare a shortlist with the bulk domain checker: add your names, pick .si, .ai and .com, and see every combination in one table.
4. Check every extension for your favourite on the domain search, which covers 150+ endings including .si.
5. Check the social handles on the username checker so your brand matches on X, LinkedIn, GitHub and Instagram.
6. Register straight away. In a rush like this one, a name that's free in the morning can be gone by the evening.

Naming patterns that work on .si

If your .si is taken

Try a small variation (get, try, use, labs, hq), check whether the .ai or .com is free instead, or find out whether the name is actually in use. The domain expiration checker shows a taken domain's expiry date and status, and how to find out who owns a domain explains how to contact an owner about buying it.

Risks to weigh before building on .si

A .si is a smart, low-cost registration for most AI brands. Go in with your eyes open about the trade-offs.

• Trend risk: if "SI" fades as a term, a .si could look dated. A neutral .com or your main .ai protects you.
• Country-code rules: .si is governed by Slovenia's registry, which sets its own policies. Read the current terms at your registrar; rules can change.
• SEO targeting: as above, Google treats .si as Slovenian at the time of writing.
• Lookalikes and scams: security researchers have reported new .si domains containing words like "bank", "pay" and "gov" since the rush began. Register your brand's .si defensively, and treat unexpected links ending in .si with the same care as any other.
• Speculators: some investors are registering names in bulk to resell; names like spacexsi.si and xai.si were parked on marketplaces within days (who owns spacex.si and x.si). Username squatting covers the same behaviour on social platforms, and the defence is the same: claim your name early.
• Lapsing by accident: a name in a hot extension gets snapped up quickly if it expires. Turn on auto-renew; what happens when a domain expires explains the timeline.

How to register a .si domain

Registering a .si works like registering any other domain. Our step-by-step guide to buying a domain covers the whole process; these are the .si-specific points.

1. Search the name on the .si domain checker and press Register when it's free.
2. Check the requirements your registrar shows for .si at checkout. Country-code registries set their own eligibility rules, so confirm you meet the current ones before paying.
3. Compare the first-year and renewal price, and choose a term.
4. Register it in your own account, not a developer's or agency's.
5. Turn on auto-renew and keep your payment card up to date.
6. Grab the matching .ai and .com if they're free, and redirect them to your main site.

Privacy on .si

Some registrars don't offer their WHOIS privacy add-on for .si (Namecheap's .si page listed it as not supported at the time of writing). As an EU registry, .si is covered by GDPR, so personal details of individual registrants are normally not shown publicly anyway, but check what will be visible before you register.

Conclusion

Recap

A .si domain is Slovenia's country code, run by Register.si, and in 2026 it became the super intelligence domain as "SI" took off as shorthand for advanced AI. New registrations jumped more than tenfold in a month, short names are still available, and a standard .si costs far less than a .ai.

It's a strong, cheap registration for AI-first brands, with real trade-offs: Google currently treats .si as a Slovenian domain, the term could fade, and country-code rules are set locally. For most founders the answer is to own both the .si and the .ai (or .com) and decide which to lead with.

Final thoughts

Start on the .si domain checker to see if your name is free, compare it with the .ai domain checker and .com domain checker, and register the winners the same day. Then lock in the matching handles with the brand name checker. For more on choosing an ending, see the best domain extensions for 2027.

Frequently asked questions