The Surprisingly Complex History of Hyphens in Domain Names

Ever wondered how many hyphens you can stack together in a domain name? I did. What started as a casual question led me down a rabbit hole through decades of Internet standards — and the answer is far more interesting than you might expect.

A Quick Answer (It's Not Simple)

In theory, you could have up to 59 consecutive hyphens in a domain name. But in practice? It's complicated. The answer depends on which RFC you're referencing, which TLD registry you're dealing with, and apparently, whether anyone bothered to enforce the rules over the past 25 years.

The Long Strange Trip Through Internet History

Let's rewind. Way back in 1978, the early Internet standards described the hyphen character as "minus" rather than hyphen. RFC 608 specified that host names could use letters, digits, and the minus sign — with only two real restrictions: the first character had to be a letter, and the last character could NOT be a minus sign.

By 1981, this was formalized in RFC 810, which described domain name syntax using what now looks like ancient programming notation: <name> ::= <let>[*[<let-or-digit-or-hyphen>]<let-or-digit>]. Translation: start with a letter, end with a letter or digit, and put whatever you want in between.

RFC 952 in 1989 carried this forward with slightly cleaner language. Then came RFC 1035 in 1987, which is often cited as the "preferred name syntax" standard. It confirmed: labels must start with a letter, end with a letter or digit, and can only contain letters, digits, and hyphens internally.

Notice what's missing? No restriction on the number of hyphens.

The IDN Twist

Everything stayed pretty stable until 2010, when Internationalized Domain Names (IDN) entered the scene. These use the xn-- prefix to enable non-ASCII characters. This is where things get interesting.

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

Why? Because xn-- looks like -- in positions 3-4. The rule exists to prevent confusion. If your domain starts with xn, you're in the clear. Everyone else? Two hyphens in positions 3 and 4 are banned.

So theoretically, you can have up to 59 consecutive hyphens by starting them at position 4 and ending at position 62. Something like abc---[…]---z.com should work fine.

Or should it?

Reality Bites: TLD Restrictions

Here's the thing about standards — they're just recommendations until someone enforces them. Each Top Level Domain registry can set its own policies, often more restrictive than the RFCs.

Some registries ban certain words. Some refuse IDN registrations entirely. Some prevent impersonation of public suffixes.

And then there's South Sudan's .ss registry, which reportedly refuses to allow any hyphens at all. Zero. None. Not even one.

Nominet, which administers .uk, doesn't have hyphen restrictions per se, but they don't allow xn-- domains.

In general, most registries will let you register multi-hyphenated domains — but "most" isn't "all."

The Anomalies: Domains That Shouldn't Exist

Here's where it gets fun. The Internet runs on a lot of legacy systems, edge cases, and "close enough" implementations. Someone decided to do some digging and found hundreds of domain names that violate modern rules.

Some highlights from the research:

• 0-------------------------------------------------------------0.com — created in 1999, now down
• 0-------------------------------------------------------------5.com — created in 2001, still live
• a-------------------------------------------------------------a.com — 61 hyphens. Yes, sixty-one. The maximum possible. This website still works and looks like it hasn't been updated since 2000.

That's right. A domain with 61 consecutive hyphens resolves to a live website in 2024.

There's also zz--icann-monitoring.uk, registered in 2024 — long after the IDN rules were established. But since Nominet doesn't allow xn-- domains, this one technically complies.

Other notable entries include domains that look like randomly generated strings, possibly used for command-and-control servers. The patterns are fascinating if you're into that sort of thing.

What Does This Mean for You?

Honestly? Probably nothing. Most domain registrars will prevent you from registering something ridiculous anyway. But understanding these rules matters if you're:

• Building domain validation into your applications
• Working with internationalized domains and need to understand the xn-- exception
• Auditing existing infrastructure for compliance issues
• Just curious about how the Internet actually works under the hood

The Internet's standards are living documents, evolved over decades by people solving real problems at the time. The hyphen rules reflect a balance between flexibility and clarity — and like most human systems, they've accumulated their share of quirks along the way.

Next time you're picking a domain name, maybe stick with something simple and memorable. But now you know: if you really wanted to, you could technically register hello------------------------------------------world.com.

You probably shouldn't. But you could.

What's the wildest domain name you've ever encountered? Drop it in the comments — I'm genuinely curious what other anomalies are lurking out there.