How do you look up postal codes?

In the United States, the best way to look up postal codes is by using the United States Postal Service web site. USPS.com provides the option to look up the zip code by address or the city or cities within a zip code the searcher provides.

For international addresses, if the country is known, postal codes or their corresponding cities can be found using the web site of that country's postal service. If neither the address or country is known, the postal code can be entered into a postal code search such as GeoNames, or, in some cases, the country can be determined based on the format of the postal code.