The Wild, Weird World of Hyphens in Domain Names

Let me ask you something: what's the maximum number of hyphens you can stuff into a domain name?

I didn't know either — until I fell down an internet rabbit hole and emerged with a story that's equal parts technical deep-dive and time capsule from the early web.

The Short Answer (Spoiler: It Depends)

Theoretically? You could string together 59 consecutive hyphens and still technically have a valid domain name.

But here's the thing: "theoretically" does a lot of heavy lifting in that sentence. The reality is messier. Your mileage varies depending on which technical standard you're looking at, which domain registry you're dealing with, and — apparently — whether anyone has bothered to enforce the rules since the 1990s.

A Little Trip Through Internet Archaeology

Let's travel back to 1978. The internet was still figuring itself out, and early standards documents described the hyphen character as "minus" — because of course they did.

RFC 608 laid out the rules for host names: you could use letters, digits, and the minus sign. Two main constraints: the first character had to be a letter, and the last character absolutely could not be a minus.

Jump ahead to 1981 and RFC 810. The syntax got formalized using what now looks like programmer poetry: <name> ::= <let>[*[<let-or-digit-or-hyphen>]<let-or-digit>]. What does this mean in plain English? Start with a letter. End with a letter or digit. Put whatever you want in the middle.

RFC 952 from 1989 cleaned up the language slightly. Then RFC 1035 in 1987 — this one gets cited a lot as the "preferred name syntax" — reinforced the same basic idea: labels begin with a letter, finish with a letter or digit, and the middle can contain letters, digits, and hyphens.

Notice something? Nowhere in any of these documents is there a limit on hyphens.

Then Everything Got Complicated: Enter IDN

The rules stayed relatively stable for decades. Then came Internationalized Domain Names in 2010.

IDNs use an xn-- prefix to support non-ASCII characters — like umlauts, accented letters, or entirely different alphabets. This is where the hyphen situation got interesting.

RFC 5891 introduced a new constraint: "The Unicode string MUST NOT contain '--' (two consecutive hyphens) in the third and fourth character positions."

Why? Because xn-- uses positions 3-4. The rule exists to prevent ambiguity. If your domain starts with xn, you're fine. Everyone else? Two hyphens in positions 3 and 4 are strictly forbidden.

So if you wanted to get creative, you could technically start your hyphens at position 4 and go all the way to position 62 — giving you a theoretical maximum of 59 consecutive hyphens.

Or at least, that's the theory.

The Real World Has Other Ideas

Here's a hard truth about internet standards: they're suggestions until someone decides to enforce them.

Every Top Level Domain registry sets its own rules, and those rules are often stricter than what the RFCs demand.

Some registries block specific words. Some won't allow IDN registrations at all. Some are designed to prevent look-alike domains that could fool users.

And then there's South Sudan's .ss registry, which reportedly allows exactly zero hyphens. None. Not even one. Just clean, hyphen-free domain names.

Nominet, which runs .uk domains, doesn't have explicit hyphen restrictions — but they don't permit xn-- domains at all, which creates its own set of complications.

Most registries will let you register domains with multiple hyphens. But "most" isn't "all."

The Hall of Weird: Domains That Break the Rules

This is where things get fun. The internet is held together with legacy code, creative interpretations, and sheer luck. Researchers have uncovered hundreds of domain names that violate current standards — yet exist anyway.

Some highlights:

• 0-------------------------------------------------------------0.com — registered in 1999, currently down
• 0-------------------------------------------------------------5.com — registered in 2001, still resolving
• a-------------------------------------------------------------a.com — 61 hyphens. Sixty-one. The absolute maximum allowed. This site still loads and looks exactly like a 2000s internet artifact.

That's wild to think about: a domain with 61 consecutive hyphens is out there, live, in 2024.

There's also zz--icann-monitoring.uk, registered in 2024 — well after IDN rules were established. But since Nominet blocks xn-- domains, this one technically complies with their specific requirements.

Other finds include domains that look like random character soup, possibly used for command-and-control operations or other less-savory purposes. The patterns are genuinely fascinating if you're into that sort of thing.

Should You Care?

Probably not on a day-to-day basis. Most registrars won't let you register something absurd in the first place.

But knowing these rules matters if you're:

• Building domain validation into applications
• Working with internationalized domains and need to wrap your head around the xn-- edge case
• Auditing existing infrastructure for compliance
• Just geeking out about how the internet actually functions

The internet's standards are living documents — layers of decisions made over decades by people solving problems in real-time. The hyphen rules represent a balance between flexibility and clarity. And like any human system, they've picked up their share of quirks along the way.

The Bottom Line

Next time you're registering a domain, keep it simple. Memorable is better than maximum hyphenation.

But now you know: if you were so inclined, you could theoretically register something like hello------------------------------------------world.com.

You almost certainly shouldn't.

But the internet would let you.