US ZipCode

About US ZipCode

The US ZIP Code API from Smarty is a web service for looking up and verifying combinations of city, state, and ZIP Code. It accepts requests via HTTP GET for single inputs or HTTP POST for multiple inputs (up to 100 inputs or 16K per request), with input fields such as city, state, and zipcode sent as query string parameters or JSON objects.

The API supports two authentication methods: "embedded key" authentication, which restricts requests to GET only, and "secret key" authentication, which allows both GET and POST. Requests are made over HTTPS only, as non-secure HTTP requests are not supported.

The product is offered alongside other Smarty APIs (address verification, autocomplete, geocoding, and enrichment) and includes an on-premise deployment option. Documentation includes an API reference, a live API playground, and SDKs for languages including .NET, Go, iOS, Java, JavaScript, PHP, Python, Ruby, and Rust.

Key features

• Look up and verify city, state, and ZIP Code combinations
• Supports GET requests for single input and POST requests for up to 100 inputs per request
• Accepts city, state, and zipcode as query parameters
• Requires auth-id and auth-token for authentication
• Supports embedded key and secret key authentication methods

Frequently asked questions