Question 1

Where does the ZIP code data come from, and how often is it updated?

Accepted Answer

The data comes from official USPS Postal Bulletins. The database holds 43,623 active ZIP codes with city, state and coordinates. Each new bulletin is processed within 7 days of publication, which covers new ZIP codes, boundary realignments, city name changes and post office closures.

Question 2

What does a response with "found": false mean?

Accepted Answer

A miss is not an error. The request was valid and no record matched, so the response is HTTP 200 with "success": true and "found": false. Reserve error handling for 4xx and 5xx codes, and treat "found" as the data question. All timings are reported in the X-Response-Time and Server-Timing headers.

US Zip Code Radius and Lookup

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