A dotless IP address is a standard xxx.xxx.xxx.xxx IP address represented as either a decimal DWORD, hexadecimal, or octal. Windows internet browsers, such as Microsoft Internet Explorer and Netscape, are able to decode such addresses to their correct IP's. In MSIE 4.x, there was a security vulnerability that would make any dotless IP address apear as if it was on the user's intranet, which was set to the lowest level of security protection within the browser.

An example of this is as follows:

E2's address is http://www.everything2.com . Its IP address is . Its dotless IP address in DWORD is http://3467251331 . All three addresses take you to the same place.