The U.S. Postal Service provides a suite of USPS Web Tools that customers may integrate into their own websites to validate or find mailing addresses, track and confirm mail delivery, calculate shipping rates, and create domestic or international shipping labels.
The Address Standardization service helps users ensure efficient delivery by standardizing street addresses, correcting abbreviations, adding missing information, and adding ZIP codes.
The ZIP Code Lookup service can determine the ZIP Code or ZIP Code+4 for an address where the city and state are known.
The City/State Lookup service can determine the city and state associated with a given ZIP Code or ZIP Code+4.