Reverse Telephone Directory
A reverse telephone directory is a type of directory used in telephony to identify a person and his/her address by entering his/her phone number. A reverse telephone directory is the opposite of traditional telephone directories, such as Yellow Pages or caller ID, which allow a user to search for a person’s phone number by entering his/her name or address. Reverse telephone directories can be useful in situations in which a phone number is available, via caller ID or another source, but a name is not. Although many commercial reverse telephone directories exist that claim to provide users with everything that is known about a particular phone number, such as the user’s home address and even billing history, many free reverse telephone directories are also available.
How Reverse Telephone Directories Work
In the days before instant Internet access, telephone companies provided libraries and police departments with “reverse white pages”, which listed every phone number that they hosted in the area in numerical order. When the Internet became available, it provided telephone companies with a much more convenient and cost-effective method of publishing these numbers for anyone who wished to see them. Now, a user anywhere in the world can run a search for a phone number as easily as any other search. While users can simply enter phone numbers into search engines, such as Google and Yahoo, dedicated reverse telephone directories compile lists of numbers directly from telephone companies and search within their own database when a user runs a search.
Applications
A reverse telephone directory is useful when a user has a phone number without a name, or has both a phone number and a name but cannot remember who the person is. Reverse telephone directories are often used when a user has an unrecognized phone number in his/her recent calls list, written down on a piece of paper, or on his/her telephone bill. Popular, free reverse telephone directories are WhitePages.com, Anywho.com, and Addresses.com.

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