Free reverse telephone number lookup is a relatively new phenomenon; it used to require a separate paper directory or toll call. Online, you can perform a free reverse lookup as quickly as a standard by-name lookup -- but online directories are a minefield of scams and pitches for paid services. Stick with the official White Pages for a safe reverse directory lookup.
Open a Web browser and navigate to whitepages.com.
Click on the "Reverse Phone" tab.
Enter the phone number in the "Find" field. Type all the numbers together -- 2125551212 -- or separate them with hyphens -- 212-555-1212. Click "Find."