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US ZipCode

The US ZIP Code API validates and looks up city, state, and ZIP Code combinations, returning standardized address information for a single query (GET) or up to 100 queries (POST).

Geocoding

apiKeyQuery

HTTPS

CORS: Yes

Description enriched …

Visit official documentation

Latency

398ms p95

Uptime

100.0% 30d

Playground

Verified

live

Endpoints

REST · JSON

GET

/lookup

Lookup city, state, and ZIP Code combinations (single input).

auth-id (query, required) — Authentication ID for the account.
auth-token (query, required) — Authentication token (secret) for the account.
city (query) — The city name (max 64 characters).
state (query) — State name or two‑letter abbreviation (max 32 characters).
zipcode (query) — The ZIP Code (max 16 characters).
input_id (query) — A unique identifier for the address used in your application; passed through to the output.

POST

/lookup

Lookup city, state, and ZIP Code combinations (multiple inputs).

auth-id (query, required) — Authentication ID for the account.
auth-token (query, required) — Authentication token (secret) for the account.

2 endpoints auto-detected

Authentication

This API uses an API key, passed as the "auth-id" query parameter. No OAuth required.

curl -X GET \
  "https://www.smarty.com/docs/cloud/us-zipcode-api/lookup?auth-id=YOUR_API_KEY"