What is a .si domain?

.si is the country code top-level domain (ccTLD) for Slovenia. It has existed since 1992 and is run by ARNES, the Academic and Research Network of Slovenia. In September 2026 it suddenly became popular worldwide because "SI" is also short for "super intelligence".

Which country does .si belong to?

.si is Slovenia's country code domain extension. The letters come from Slovenija, the country's name in Slovenian, and match its official ISO country code. That's why websites in Slovenia use .si, much like websites in Germany use .de and those in the UK use .co.uk.

The .si domain was added to the internet's root zone on 1 April 1992 and is managed by ARNES, the organisation responsible for Slovenia's national domain registry. Through register.si, ARNES oversees the registration and administration of all .si domain names.

For many years, .si was used mainly by businesses, organisations and individuals in Slovenia. It has also attracted fans of creative domain names and domain hacks. In Slovenian, "si" means "you are", while the Spanish word "sí" means "yes", making .si a memorable choice for branding. Well-known examples include jit.si, the web address used by the video-calling platform Jitsi, and pep.si, which Pepsi has used as a short link.

More recently, .si has gained wider attention as "SI" has emerged as shorthand for "super intelligence", introducing the extension to a new audience beyond its traditional Slovenian roots.

Why is everyone suddenly registering .si domains?

Interest in .si surged on 22 September 2026, when US President Donald Trump told the United Nations General Assembly that the US government would use the term "super intelligence" instead of artificial intelligence. The abbreviation, SI, happens to be the same as Slovenia's domain extension.

Within days, thousands of .si domains were registered. According to industry publication Domain Name Wire, many of the registrations came from domain investors betting that .si names could rise in value if "SI" gains wider adoption.

The growth was dramatic. The .si registry recorded around 3,500 new registrations during the whole of August 2026. After the speech, more than that were registered on most individual days. By 30 September, the total number of .si domains had climbed to nearly 229,000, up from around 190,000 at the start of the month.

Interest in .si had been growing even before September. Earlier in 2026, domain investors were already registering .si names on the assumption that "SI" could become a recognised abbreviation for super intelligence, a term used in AI research to describe systems that surpass human intelligence.

Whether .si will follow the same path as .ai remains to be seen. The popularity of .ai was driven by companies actively using it for their websites. For .si, long-term success will depend less on how many domains are registered and more on whether businesses choose to build their brands on it.

Want a .si domain name before someone else takes it?

Is a .si domain safe?

Absolutely! .si is an established national domain extension with more than 30 years of history, managed by a public institution. It's not a new or experimental domain, and .si websites and email addresses work just like those using .com or .co.uk.

The .si registry also includes the safeguards you'd expect from a well-managed country-code domain:

• DNSSEC, which helps prevent visitors from being redirected to fake versions of a website.
• An Alternative Dispute Resolution (ADR) process, allowing someone with stronger rights to a domain name, such as a trademark owner, to challenge a registration without going through the courts.
• Published policies and procedures covering domain registration, renewals and data protection.

That said, no domain extension is automatically trustworthy. A website's security depends on how it's managed, including the use of an SSL certificate (so the address starts with https), up-to-date software and legitimate content. As with any domain extension, a surge in popularity can attract opportunistic websites, so it's always worth checking a site's authenticity before sharing personal information.

Who can register a .si domain?

Almost anyone can register a .si domain. The registry's terms define a domain holder simply as a "natural or legal person", which means both individuals and organisations are eligible. There's no requirement to live in Slovenia or operate a Slovenian business, and domains are assigned on a first-come, first-served basis.

A .si domain must meet a few basic requirements:

• It must be between 2 and 63 characters long.
• It can't begin or end with a hyphen.
• Domains are registered directly under .si, such as yourname.si.
• A small number of names are reserved. Domains including 112.si, 113.si, si.si and rs.si are set aside for Slovenian government and emergency services.

At the registry, a .si domain can be registered for one year at a time and renewed as long as you like. You can check which names are still free on our .si domain page.

Will a .si domain help or hurt your SEO?

A .si domain won't boost your search rankings by itself. Search engines rank websites based on factors such as content quality, relevance and links, not the domain extension at the end of the web address.

There is, however, one thing to consider if you're planning to use .si for a business outside Slovenia. Most country-code domains are treated by Google as a signal that a website is intended for users in that country. While Google considers some country-code extensions, such as .ai, .io, .co and .tv, to be generic, .si isn't one of them. As a result, a .si website is generally seen as targeting Slovenia.

That's a clear advantage if your audience is in Slovenia, but it may be less helpful if you're targeting customers elsewhere.

If your focus is the UK or another international market, it often makes sense to use a .si domain alongside your main website rather than replacing it. You can redirect the .si domain to your primary site or use it for a specific product, campaign or project.

Should you get a .si domain?

A .si domain could be a good choice if:

• You do business in Slovenia, or plan to, and want a web address that local customers will immediately recognise.
• You're building an AI-related brand or product and like the connection to "SI". Registering a name now gives you more flexibility while the term is still emerging.
• You want to protect your brand. When a domain extension suddenly attracts attention, securing yourname.si can help prevent someone else from registering it first.
• You enjoy clever domain hacks that play on the meanings of "si", such as "you are" in Slovenian or "yes" in Spanish.

A .si domain may be less suitable if it would be your only domain and most of your customers are outside Slovenia. In that case, it's usually better to keep a .com, .co.uk or another relevant local domain as your primary web address.

And if you're considering registering .si domains purely for resale, keep in mind that domain values depend on future demand, which is impossible to predict with certainty.

So, what is a .si domain?

• .si is Slovenia's official country code domain extension. It has been in use since 1992 and is managed by the national registry ARNES.
• It attracted global attention in September 2026 after "SI" emerged as shorthand for "super intelligence".
• It's a well-established, secure domain extension, with features such as DNSSEC and a dispute resolution process.
• Anyone can register a .si domain, regardless of where they live or operate, on a first-come, first-served basis.
• Google treats .si as a Slovenia-focused domain, so if your audience is elsewhere, it's often best used alongside your main domain rather than as a replacement.

Frequently asked questions

What does .si stand for?

.si stands for Slovenia. The two letters come from Slovenija, the country's name in Slovene, and match Slovenia's official ISO country code, SI. Like most country code domain extensions, .si is based on an ISO country code, just as .de represents Germany and .fr represents France.

What is the .si domain used for?

.si is used mainly by Slovenian businesses, public organisations and individuals, much like .de is used in Germany. It's also popular for domain hacks, as "si" means "you are" in Slovene and "yes" in Spanish. In 2026, interest in .si grew beyond Slovenia as some AI companies and domain investors began registering .si names in connection with the term "super intelligence".

Does .si mean super intelligence?

No, .si is, and remains, Slovenia's official country code domain extension. The connection to "super intelligence" comes from the abbreviation SI, which gained attention after the US government announced in September 2026 that it would use the term "super intelligence" for AI. The .si domain itself hasn't changed, and neither have the registry or its registration rules.

Is .si a generic domain like .ai or .io?

No. While Google treats .ai and .io as generic domain extensions, .si is not included on Google's list of generic country-code domains. As a result, Google generally sees a .si website as targeting Slovenia. That can be an advantage if you're trying to reach Slovenian customers, but it may be less helpful if your audience is based elsewhere. If your business operates outside Slovenia, it's usually best to use .si alongside your main domain rather than as a replacement.

Can I use a .si domain for email?

Yes. A .si domain works just like any other domain for email, so you can create addresses such as hello@yourname.si. All you need is an email service connected to your domain.

With growing interest in "super intelligence", a .si email address can be a good fit for an AI-focused brand. For most businesses outside Slovenia, however, a more familiar domain extension may be easier for customers to recognise and remember.

How long can I register a .si domain for?

At one.com, domains are currently available with a one-year registration term only, but you can continue renewing your domain for as long as you want to keep it. The registration period starts on the day the domain is registered.

Is .si the same as SI units?

No. The two are completely unrelated. SI units, such as metres, kilograms and seconds, take their name from the French term Système international d'unités. .si, on the other hand, is Slovenia's country code domain extension.

The only connection is that they share the same two letters, which is why searches for ".si" can sometimes return results about both.