How to Look Up a Phone Number and Run a Reverse Search

phone number search

In almost every investigation case, a private investigator will have a need to look up a phone number. Investigators run phone number searches during missing person investigations, as part of a background check, to locate a witness or expert and as a part of everyday business. This article provides a list of the top sites for conducting online searches and how to get the best results.

How to Search for a Phone Number

  • Before the internet, people had to rely on printed telephone directories to look up numbers. If you wanted to find a number outside of your local area, you had to visit the local library, or travel to the library in another city or state. Now, public telephone directories are available as online databases and can be accessed quickly via computer, tablet or mobile device. There are a number of websites that provide searchable versions of the white pagesand yellow pages. Multiple numbers can be searched at no cost. Following are some of the more popular sites.
  • BigBook– BigBook provides access to the complete Yellow Pages (and business white pages) for the United States. It has a nice feature of a map interface that can plot an address to street level, or select phone numbers in a mapped area.
  • The Internet 800 Directory– This site provides a large collection of toll-free numbers, includes non-AT & T customers.
  • Lookup USA– Lookup USA is a national directory of people and businesses as well as a classified directory. Their unique feature is credit ratings for most of the 10 million business telephone number listings. Has street maps also.
  • com– was created with the goal of creating a community-driven website that allows people to post annoying callers, and telemarketers.
  • Pay Phone Directory– Pay Telephones have been slowly phasing out, but some still exist. The Pay Phone Directory website offers thousands of pay telephone numbers in the United States, Canada, and other countries.
  • Phone Validator– The Phone Validator is a useful tool that allows users to learn if a phone number is a landline or a cell phone.  The site also allows users to automatically run the phone number through directory assistance and Google to develop new leads.
  • Spokeo People Search– Spokeo is a people search engine that specializes in aggregating and organizing vast quantities of people-related information from a large variety of public sources. The public data is amassed and presented in an integrated, coherent, and easy-to-follow format. It is a great resource for private investigators.
  • Switchboard USA White Pages– Switchboard is a complete national directory that can be used for looking up both private numbers and business numbers.
  • com– This site is a global directory with index of e-mail addresses and phone numbers.
  • WhoWhere– WhoWhere is a website that provides access to both business and residential numbers for the USA. Search by name and location.
  • com– Private detectives can use this website to search for businesses through the yellow pages business phone book.
  • U S West Dex– Dex is one of the leading Yellow Pages publishers. A leader in local search, Dex connects business and consumers through its portfolio of print solutions and online at

How to Get the Best Results

There are a few time-saving tricks that will help you save time and get more accurate results.

See White Pages for more resources.

What is a Reverse Search?

A reverse search is used when you have the phone number and need to match it to a physical address. Again, most of the online white page and yellow page search sites listed above offer this capability. Just type in the number and hit enter.

How to Find Unlisted Numbers

There is no easy way to find unlisted phone numbers. Individuals who don’t want their phone number listed in the telephone directory do so for a reason. They prefer to remain anonymous and avoid many of the calls from telemarketers and scammers. Some database information providers (such as X, Y, Z) compile contact information from alternative sources such as (X,Y, Z). Paying to access such services will increase the likelihood of a match.


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