Reverse Phone Lookup
(also known as a gray pages directory, or criss-cross directory ) is a collection of telephone numbers and associated customer details. However, unlike a standard telephone directory, where the user uses customer's details (such as name and address) in order to retrieve the telephone number of that person or business, a reverse telephone directory allows users to search by a telephone service number in order to retrieve the customer details for that service.
Reverse telephone directories are used by law enforcement and other emergency services in order to determine the origin of any request for assistance, however these systems include both publicly accessible (listed) and private (unlisted) services. As such, these directories are restricted to internal use only. Some forms of city directories provide this form of lookup for listed services by phone number, along with address cross-referencing.
Publicly accessible reverse telephone directories may be provided as part of the standard directory services from the telecommunications carrier in some countries.
Printed reverse phone directories have been produced by the telephone companies (in the United States) for decades, and were distributed to the phone companies, law enforcement, and public libraries. In the early 1990s, businesses started offering reverse telephone lookups for fees, and by the early 2000s advertising-based reverse directories were available online, prompting occasional alarms about privacy concerns.
In the United States, landline phone subscribers can pay a small fee to exclude their number from the directory. This service is usually called "Your Listing Not Published" and the cost ranges between $0.80 and $1.50 for residential customers.
As cellular phones become more popular, there has been debate about releasing cell phone numbers into public 411 and reverse number directories. (S. 1963, the "Wireless 411 Privacy Act" 9/2004). However, opposition led by leading consumer-protection organization Consumers Union presented several privacy concerns in their congressional testimony. Right now,[when?] cell phone numbers are not available in any public 411 or reverse-number directories. However, several information companies provide reverse cell phone lookups that are obtained from utility resources, and are available online. Because there is no central database of cell phone numbers, reverse phone directories that claim to be free cannot return information on those numbers.
In recent years, community web based services offer a reverse telephone directory of known telemarketers, debt collectors, fund raisers, and other solicitors which contact consumers by telephone. Users of these services can perform a search of the telephone number which showed up on their caller ID and read through user comments to find the identity of the calling company or individual.