The U.S. Postal Service features a ZIP code look-up option on its website. The user enters the street address, city and state and clicks the Find button. The USPS website then returns the ZIP code associated with the address.
The search results provide the ZIP+4 for the address. The extra four-digit number at the end of the ZIP code narrows down the location of the address to a small area within the city, such as a block or an apartment building.
The USPS ZIP code look-up feature also allows users to search for ZIP codes for companies. The user enters the address information plus the company name on the search page. The third tab on the search page allows users to search for a city based on a ZIP code.