Should I use capitalization when mentioning a domain name?
Editor of the Jargon File here. If there is an authority on this question, I'm it.
Never capitalize domain names unless you know for certain they were registered with that exact capitalization. In practice this means: Never, ever capitalize. If these means you have to rewrite a sentence to avoid having a domain name at the beginning, do so.
The more general rule, which explains this one, is: never capitalize any name with a case-sensitive encoding. Other cases this includes are variable names in mathematical formulas and computer programs, and names of programs on operating systems (like Unix) with case-sensitive filenames.
(Some people will reply that domain names are not case-sensitive. In the new Unicode world this is no longer true. And even in older times, interfaces that expected domain names - including embedding in URLs - were often case-sensitive.)
The reason for this rule is that you never want to mislead humans into remembering and using a case variant that a literal-minded computer will not accept.
I don't think there is a correct answer for this question. It's a matter of style: you decide what to do each time.
I've googled 4 famous brands and visited their page on Wikipedia, their websites were written like this:
- Site.com
- site.com
- www.site.com
- http://site.com
As you can see, everyone adopted a different format. It might depend on the site's specific URL, but putting that aside, in the first two the choice for the capitalization is not on "correctness".
Just a note: If you write it one way in a document, keep that logic everywhere in that document. This would be the only rule: be consistent in your own writing.
From an IT standpoint the generally observed customs are:
- As a general rule domain names are written in lower case.
This transcends other conventions like capitalizing abbreviations/"initialisms" - for example the IANA website is referred to as "www.iana.org" - It is preferable to let the domain name stand alone the way you would type it in a URL bar.
For example "The new acme.com website" rather than "acme.com's new look"
This one is not universally observed, and is often disregarded if the possessive form "sounds better". - Avoid starting sentences with a domain name (to avoid the capitalization issue)
(A simliar convention is observed when discussing operating system commands that are case-sensitive.) - In marketing documentation it's acceptable to capitalize the domain name in a manner consistent with the brand (e.g. "Acme.com", "PremierHeart.com").
- If it is included as part of the domain name "www" is written in lowercase, not as "WWW" and under no circumstances as "Www" (which looks utterly ridiculous).
That said, as others have pointed out it's probably more important to be consistent.
There is an important distinction to make here.
One, a domain name is traditionally written in lower-case even though it is case-insensitive. So if you are writing a URL (or a domain name that is meant to represent a url) you should probably write it in lower-case.
If you are writing the name of a company, or a product, or some other proper noun, that proper noun will have its own rules of capitalization. So you'd write Sony but not Sony.com.
Some companies are named the same as their domains. In this case there might be different rules depending on whether you are referring to the domain or to the company. The company itself might request that you always write both names the same way, even if that means upper-casing a domain name. However, I don't think it's incorrect from a style perspective to always lower-case web addresses.
The most important thing is to be consistent.