The United States Postal Service provides a free postal code look-up on its website, USPS.com. To search, go to the Quick Tools menu, and in the drop down select Look Up a ZIP Code.
USPS.com also allows users to search for ZIP codes by company name and to look up the city name for a ZIP code.
Other countries also provide free postal code look-up tools. Canada provides a postal code look-up on its website, CanadaPost.ca. To search this site, go to the Tools menu and click on Find a Postal Code. The United Kingdom Royal Mail also has a look-up on its website, RoyalMail.com. Click on the Sending Mail menu, and then click Find a Postcode.