Domain names that start with a number

Asked Dec 04 '17 at 16:15

Active Dec 04 '17 at 16:15

Viewed 4,891 times

I'm writing a regex for validating domain names. I'm looking at section 2.3.1 (starts on the bottom of page 7) and in the section it states:

They must start with a letter, end with a letter or digit, and have as interior characters only letters, digits, and hyphen. There are also some restrictions on the length. Labels must be 63 characters or less.

But I've seen domains all over the place that have digits as the leading character? Is there another RFC that I am missing that changes this?

edited Oct 07 '21 at 11:02

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asked Dec 04 '17 at 16:15

wheeler

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https://serverfault.com/questions/638260/is-it-valid-for-a-hostname-to-start-with-a-digit – Barmar Dec 04 '17 at 16:39
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RFC 1123 updated it to allow leading digits. – Barmar Dec 04 '17 at 16:39

Domain names that start with a number

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