Nominatim vs OpenStreetMap

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.

The core OpenStreetMap API serves and edits the raw map database underlying OSM — nodes, ways, and relations — over HTTPS at api.openstreetmap.org. Reading map data requires no authentication at all, while creating or modifying data requires an OAuth 2.0 token tied to an OSM account (the older Basic Auth/OAuth 1.0a login methods were retired in June 2024). It's a general-purpose data API rather than a geocoding service specifically — OSM points address-lookup users to the separate Nominatim service, and bulk-read users to Overpass.