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."
If a White Pages reverse lookup doesn't yield results, a general Internet search, such as with Google, Bing or Yahoo, may be your best bet. Be aware, however, that many search results may lead to sites that require payment but provide no promise of relevant information.