M
API Matrix

US ZipCode API

⭐ Beginner's Pick Geocoding / API Key Intermediate HTTPS CORS
Varies by plan (check documentation)
47 Score
Grade D
Visit Official Site Compare Alternatives

Overview

The US ZipCode API by Smarty validates US zip codes and returns detailed geographic data such as city, state, county, and lat/lng coordinates. It is useful for checking whether a zip code is valid and enriching address data in forms or databases. A free tier is available to get started quickly.

💡

Beginner Tip

Pass your auth credentials as query parameters auth-id and auth-token. A single lookup requires just the zipcode parameter and returns all associated cities for that zip.

Available Data

US ZipCode data via REST API
JSON-formatted response data
Requires API key authentication

Example Response

JSON Response 
{
  "input": "[email protected]",
  "is_valid": true,
  "format_valid": true,
  "details": "Input passes all validation checks"
}

Field Reference

input_index Index of the input record this result corresponds to, useful for batch lookups.
zipcode The validated US zip code.
zipcode_type Type of zip code, such as S (standard), P (PO Box), or U (unique).
default_city The primary city name associated with this zip code.
state_abbreviation Two-letter US state abbreviation, e.g. CA or NY.
latitude Approximate latitude coordinate for the zip code area.

Implementation Example 

const url = "https://www.smarty.com/docs/cloud/us-zipcode-api";
// Replace headers or query params with the values required by this API.
const response = await fetch(url, {
  headers: {
  "X-API-Key": "YOUR_API_KEY"
  }
});
if (!response.ok) throw new Error(`Request failed: ${response.status}`);
const data = await response.json();
console.log(data);

What Can You Build?

Note: These code examples are AI-generated and unverified. Always refer to the official API documentation for accurate usage.

Common Errors & Troubleshooting

401 Unauthorized Missing or incorrect auth-id or auth-token parameters.
✓ Register at smarty.com and add your auth-id and auth-token as query parameters.
Empty response array The zip code does not exist or is invalid.
✓ Validate the zip code format (5 digits) before calling the API. An empty array means no match was found.
429 Too Many Requests You have exceeded your plan's monthly lookup quota.
✓ Upgrade your Smarty plan or cache results locally to reduce duplicate lookups.

Matrix Score Breakdown

🌐 Reachability 0/30
⚡ Speed 15/20
🔒 Security 15/15
🛠 Developer XP 17/20
✓ Reliability 0/15

Partially tested on Apr 5, 2026

Technical Specifications

Auth API Key
HTTPS REQUIRED
CORS YES
Category Geocoding
Difficulty Intermediate
Verified: 2026-04-04

Similar APIs

View All →

Actinia Grass GIS

0

Actinia Grass GIS provides programmatic access to actinia is an open source rest api for geographical data that uses grass gis via REST API.

API Key Intermediate HTTPS

Apiip

82

Apiip is an IP geolocation API that returns detailed location data including city, country, timezone, and currency for any IP address.

API Key Intermediate HTTPS

Battuta

22

Battuta is a hierarchical location API that lets you browse countries, regions, and cities in a cascade, making it easy to build location pickers with dependent dropdowns.

API Key Intermediate

BigDataCloud

⭐ Beginner's Pick
77

BigDataCloud offers a fast and highly accurate IP geolocation API that also includes network security checks and a confidence area metric to indicate how precise the location is.

API Key Intermediate HTTPS

Bing Maps

87

Bing Maps (now Azure Maps) is Microsoft's mapping platform that lets you geocode addresses, reverse geocode coordinates, get routes, and embed interactive maps in your applications.

API Key Intermediate HTTPS