Domain Names Are Case Insensitive

By Mike Maddaloni on Tuesday, January 27, 2009 at 04:00 AM with 3 comments

Did you know domain names are case insensitive? Had you even thought about it?

This is a question I have been asked a few times, so I thought I’d write about it and share with all. From a technical standpoint, domain names ignore case. Therefore, it you are typing in a domain name in a browser, you can use uppercase or lower case letters and it won’t matter. For a more technical description, read this article from the Internet Engineering Task Force on domain name case.

Why this question comes up is when people are presenting a domain name in print, whether in paper form or on a Web page or a PDF document. Typically this is if they want to capitalize one or more names that make up a domain name. For example, the domain name for The Hot Iron can be presented and entered into a browser as,,… you get the gist of it.

URLs May Be Case Sensitive

Despite the domain name being case insensitive, a URL may be case sensitive. The domain name portion will not be, but on some Web servers, the remainder of the URL may have both uppercase and lowercase characters, and you will need to be careful to enter them properly.

If you are planning on displaying a domain name on a billboard, be as creative as you’d like and mix character case all you want. If you are planning on displaying a URL on a banner… well, on second thought get another domain name to redirect to that URL.

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