Nominatim vs ViaCep

Nominatim provides worldwide forward and reverse geocoding built entirely on OpenStreetMap data, needing no API key — only a descriptive User-Agent or Referer header identifying the calling application. The public instance at nominatim.openstreetmap.org is a free courtesy service, not a commercial product: its usage policy caps requests at 1 per second, forbids autocomplete-style querying and bulk/parallel scripts, and requires caching results rather than re-fetching them. Heavier users are expected to self-host Nominatim against their own OSM extract instead of relying on the shared instance.

ViaCEP is a free, high-availability web service for looking up Brazilian postal codes (CEP): given an 8-digit CEP it returns street, neighborhood, city, state, and IBGE/DDD codes, with a reverse address-to-CEP search available too. It's run by WBX and widely embedded across Brazilian dev tooling — its own docs warn that heavy bulk-validation traffic against it can trigger an automatic, indefinite IP block.