What it does
Nominatim is the geocoding service used by OpenStreetMap’s search feature. Its API supports free-form or structured address searches, reverse geocoding, and place lookup by OpenStreetMap identifier. Search responses can include address components and several machine-readable formats, including JSON, GeoJSON, and GeoJSON-oriented geocoding output. The public OpenStreetMap Foundation server is intended for modest, user-triggered use under a strict usage policy; teams needing dependable or high-volume service can install Nominatim themselves or choose another provider.
Nominatim is useful when an application needs to resolve a user-entered address or place name into coordinates and an OpenStreetMap result. The documented /search endpoint accepts either a free-form q string or structured fields such as street, city, and postal code. You can request jsonv2, GeoJSON, or another supported response format, ask for address details, and constrain results by country or map area. The /reverse endpoint goes the other direction, turning a coordinate into a nearby mapped place or address.
Keep the public service within its intended use
For a user-triggered address lookup, a sensible integration requests one result set, caches repeat queries, and displays OpenStreetMap attribution. The OpenStreetMap Foundation policy for nominatim.openstreetmap.org caps use at one request per second and requires an identifying User-Agent or Referer. It prohibits client-side autocomplete, systematic place harvesting, and reselling geocoding results; products whose main purpose is geocoding must run their own service. The source data is under ODbL, which includes share-alike obligations.
The policy applies to the Foundation-hosted public instance, not every Nominatim deployment. If your workload is regular, commercial, or larger than occasional user searches, assess those terms before building around the shared endpoint; Nominatim can also be self-hosted, which is a different deployment from using the public service. Pricing for the public service was not stated in the reviewed pages.
Strengths
- A single geocoding API offers text search, reverse geocoding, and lookup by OpenStreetMap object ID.
- Search supports both natural-language address strings and structured address fields, with format and geographic filters.
- The public policy describes an open API for external use when requests remain modest and user-triggered.
Watch out for
- The public server is limited to at most one request per second and requires an identifying User-Agent or Referer plus attribution.
- Autocomplete, systematic harvesting, and resale of geocoding results are prohibited on the public instance; primary geocoding services must self-host.
- OpenStreetMap data is distributed under ODbL, whose share-alike terms may affect how derived data is reused.
Best for
- Geocoding occasional address or place searches in a modest user-facing application
- Prototyping geospatial lookup with OpenStreetMap data before deciding whether to operate a dedicated instance
Sources
- Overview - Nominatim 5.3.3 Manual (Oct 26, 2026)
- Search - Nominatim 5.3.3 Manual (Oct 26, 2026)
- Nominatim Usage Policy (aka Geocoding Policy) (Oct 26, 2026)
- Nominatim (Oct 26, 2026)