A normal “lookup” process would involve paging through the phone book and locating a business name as a means of discovering its phone number. A reverse lookup is the same process in reverse: If you have a telephone number but don’t know the name associated with it, a reverse lookup will give you the name of the person or business that corresponds with the number. The reverse lookup process can, in some cases, be applied to mailing addresses or email addresses in addition to conventional telephone numbers.

Access one of the numerous reverse lookup websites. See Resources for several examples. Note that while some reverse lookup sites will charge you a fee to see the final results, most will allow you to do the initial search, and show you partial results, for free.

Select which type of reverse lookup you intend to do, if you have the option of choosing. Some sites offer multiple types of lookups, in which case you will need to choose, while others offer only one sort of reverse lookup service.

Input the information you have on the given person or business, such as a phone number, email address or mailing address, into the appropriate field, then click the "Search" or "Find" button.