A Web address that is easy for a user and a search engine crawler to decipher. All programming code embedded in a friendly URL is hidden under abstract and more readable names. For example, the "dirty URL" to look up the definition for the term "BGA" from the Computer Language Company's hosting server for customer W432 might look like computerlanguage.com/lookup.asp?id=W432&d=BGA.

Dirty URLs are hacker prone, because a file extension, such as ASP, gives away the underlying technology, and the syntax of the URL reveals the type of request. In contrast, the friendly URL for this query might be computerlanguage.com/lookup/W432/BGA, which offers a human readable and search engine friendly address, while hiding the Web server infrastructure. See URL.