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Domain Name Rules1:32 with Jason Seifer
Different parts of a domain name mean different things and are looked-up different ways. Domain names must be formatted a certain way in order to be valid. Learn the rules for domain name formatting in this video.
- TLD: Top Level Domain, for example ".com".
- LDH Rule: Letters, digits, and hypeh. This is commonly referred to when naming domains and subdomains.
Domain Name Formatting Rules
- There are currently 326 different top level domains.
- Domain names are read right to left: subdomain(s), domain, and TLD.
- There can be up to 127 levels of a domain name.
- The full domain name may be up to 253 characters and must use the ASCII character set.
- The domain name must follow the LDH rule.
- Domain names cannot start or end with a hyphen.
There are 3 different types of top-level domains or TLDs.
There are country code top-level domains like .us,
.uk, .il as well as a ton more.
There are also generic top-level domains, which you're probably pretty familiar with.
These are things like .com, .net, .org, .gov as well as many, many more.
And finally there are infrastructure top-level domains,
which we'll get into a little bit later on in the course.
Now, there are some constraints with top-level domains.
They can never be all numeric.
Now, when you look at a website like www.example.com
you'll see that it's 3 different levels.
The top-level domain,
domain, and the subdomain.
You might be wondering how many different levels you can have in a domain name.
The answer is there can be 127 levels
each of them being up to 63 characters.
However, that could quickly get out of control.
So the full domain name is limited to 253 characters of text,
and the domain name must use the ASCII character set
and has limitations called the LDH Rule,
which stands for letters, digits, and hyphens.
This means you can use the letters A through Z in lower case or upper case,
the numbers 0 through 9,
as well as a hyphen.
And the domain name cannot start or end with a hyphen.
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