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Choosing input mode

A lookup accepts four mutually exclusive input modes. The right one depends on what data you have and how precise you need to be.

ModePrecisionWhen to use
address=Highest (SPD-aware)You have the full street address
lat=/lng=Point-precise where boundary data exists (e.g. CA, WA, NM, FL)You already have coordinates
zip=ZIP-level (lower confidence)You only have the ZIP
location=A DoR-published place nameYou have a normalised city name

For most US states, address mode is the right default — it resolves to the actual jurisdiction at the address (including Special Purpose Districts that don’t surface from ZIP alone).

If you only have the ZIP, the default response still gives you a single best-rate answer, but with a lower confidence on ZIPs that straddle jurisdiction boundaries — re-query in address mode (or with a ZIP+4) to firm it up. To see every candidate for a straddling ZIP, request mode=full.

Full content coming soon — for now, see State-specific notes for per-state precision details.