History

Let's do some history!

This is 1978's "HOST NAMES ON-LINE". Early Internet standards described the - character as "minus" rather than hyphen.

RFC 608

up to 48 characters drawn from the alphabet (A-Z),

digits (0-9), and the minus sign (-) ... specifically, no blank or space characters allowed;

no distinction between upper and lower case letters;

the first character is a letter;

the last character is NOT a minus sign;

no other restrictions on content or syntax.

So, originally, you could have as many hyphens as you wanted after the first symbol - which had to be a letter. The last symbol had to be a letter or number⁰.

That was later formalised in 1981's "DoD INTERNET HOST TABLE SPECIFICATION"

RFC 810 GRAMMATICAL HOST TABLE SPECIFICATION

<name> ::= <let>[*[<let-or-digit-or-hyphen>]<let-or-digit>]

That's carried in the the slightly more modern RFC 952.

By the time we hit 1987, the word "minus" has gone. Note, there are no restrictions on the number of hyphens - just as long as your domain name doesn't start or end with one¹.

RFC 1035 2.3.1. Preferred name syntax

The labels must follow the rules for ARPANET host names. They must start with a letter, end with a letter or digit, and have as interior characters only letters, digits, and hyphen.

By 1989, the "DOMAIN NAMES - IMPLEMENTATION AND SPECIFICATION" was tweaked again:

RFC 1123 2. GENERAL ISSUES

The syntax of a legal Internet host name was specified in RFC-952. One aspect of host name syntax is hereby changed: the restriction on the first character is relaxed to allow either a letter or a digit. Host software MUST support this more liberal syntax.

And, from then on, things stayed pretty stable until the futuristic year 2010. That was when Internationalised Domain Names (IDN) became available. They use the xn-- string at the start of the name so, the spec now says:

RFC 5891 4.2.3.1. Hyphen Restrictions

The Unicode string MUST NOT contain "--" (two consecutive hyphens) in the third and fourth character positions and MUST NOT start or end with a "-" (hyphen).

What they really mean is that "--" is banned in position 3 & 4 unless the first two characters are "xn"².

So, in theory, you can have up to 59 consecutive hyphens by ensuring that they start in position 4 and end at position 62.

Something like abc---[…]---z.com should be fine.

OR IS IT?!?!?

TLD Restrictions

There's what the RFC's say, and what a Top Level Domain (TLD) will allow. The Registry (the organisation which administers the TLD) may set their own, more restrictive, policies. Some will ban naughty words, or refuse IDN registrations, or prevent impersonation of Public Suffix domain, etc.

For example, South Sudan's .ss policies refuse to allow any hyphens.

Nominet, who run the .uk Registry, don't have any restrictions on the use of hyphens other than refusing to register xn-- domains.

But, in general, you can register multi-hyphened domain names with most Registries.

Anomalies

Of course, the mighty Internet mostly runs on spit and hope³. Naturally there are going to be mistakes, glitches, exceptions, and anomalies.

My delightful friend Q Misell had a rummage through her archives and helped track down some of the domain names which violate the modern rules. It's somewhat difficult to query every domain name, nevertheless, there are hundreds of multi-hyphened domains lurking within DNS.

Some, like ok--computer.com are long dead, but some are still active⁴!

Possibly the most consecutive hyphens belongs to http://a-------------------------------------------------------------a.com/

Sixty-one hyphens! The maximum possible, and it still works! The website looks like it hasn't been updated since it was first registered in 2000.

But what about more modern domains? The spookily named http://zz--icann-monitoring.uk/ was registered in 2024 - long after the rules were updated. But as Nominet doesn't allow xn-- domains, I guess it is fine?

There are some domains like bq--3bhauz7frjrgbka.com which look like they were pseudo-randomly generated. Perhaps as command-and-control servers?

Here's a quick table showing some of the ones Q found:

Note, "Live" just means an HTTP request returned something. There may, of course, be other services running on that domain, or on subdomains.

So What?

Without a full list of every domain name, it's rather hard to draw firm conclusions. But, in the absence of anything better to do, here are some thoughts.

• Most people don't want multiple consecutive hyphens in their domain names. They're unwieldy but mostly not prohibited.
• If the authors of RFC 5891 had access to a full list of domains, might they have chosen a different syntax for Punycode?
• Why is it so hard to look through every single registered domain name anyway? Even Certificate Logs no longer seem to be easily searchable.
• Are there any other weird restrictions which are violated by older domain names?
• When will DNS finally go all-in with Unicode rather than this kludge? (Probably around the same time as IPv6 adoption!)

If you know of any weird multi-hyphenated domains, please stick a comment in the box 😊

Update! A kind anonymous benefactor has shared a list of eighty-four thousand domains with multiple hyphens. There are some very odd entries in there.

Long-time readers of this blog will know that it's possible to register .me.ss domain names - there are various other 3rd level domains you can buy.

But, from the 1st of August 2024, you'll be able to apply for a 2nd level. So you'll be able to grab example.ss.

Here's the official announcement.

As per normal for a new TLD, there will be a period where organisations with Trade Marks can register their domains. Then a period where anyone with sufficient cash can register their cool idea for a domain. Then it opens up to everyone.

So what will they cost? Afriregister provided these prices:

For comparison, their .me.ss domains are only €25.

Registrations will only be allowed in ASCII - which means no IDNs. The majority of the languages officially recognised in South Sudan appear to be written in the Latin script, so that shouldn't be a huge issue.

As is common with all other TLDs, there is a list of words which will not be allowed to be registered.

Applications will not be accepted for domain names appearing on the Second Level Domain (SLD) block list.

When I previously investigated this, there were lots of names which weren't available due to local politics. Although there is an archived version of the list of banned words (PDF), the modern SLD Block List appears to have vanished from the registry. I've asked them for an updated list which I'll link to once I get it.

I think it is fair to say that the .ss TLD has had a tumultuous history. There hasn't been much discussion of this change in policy since the announcement a few weeks ago - but I hope that this opening up will help South Sudanese people & businesses to establish their own distinct presence on the Internet.