Nominatim

Overview

Nominatim is the geocoding engine behind OpenStreetMap: it converts place names/addresses into coordinates (forward geocoding) and coordinates back into addresses (reverse geocoding), using OSM data under the ODbL license. Free to use on the public instance — with important usage rules (see below).

Quick Start

Forward geocoding (verified live):

curl -A "my-app/1.0 (contact@example.com)" \
  "https://nominatim.openstreetmap.org/search?q=berlin&format=json&limit=1"

Reverse geocoding (what’s at these coordinates?):

curl -A "my-app/1.0 (contact@example.com)" \
  "https://nominatim.openstreetmap.org/reverse?lat=52.52&lon=13.405&format=json"

Lookup by OSM ID:

curl -A "my-app/1.0 (contact@example.com)" \
  "https://nominatim.openstreetmap.org/lookup?osm_ids=R62422&format=json"

Usage rules (important!)

• Send a descriptive User-Agent identifying your app (verified: requests without a proper UA get HTTP 403 Access denied).
• Max 1 request per second — the public instance enforces this.
• No heavy/bulk use, no commercial redistribution without a Nominatim Data Use agreement (it’s based on OSM data, ODbL).
• For heavy production use, consider running your own Nominatim instance.

What’s in the results

Each result includes lat/lon, place_id, osm_type/osm_id, display_name, type, class, importance, and address components (addresstype, address object with road/city/country…).

Authentication

None — keyless, but the User-Agent rule is effectively mandatory.

FAQ

Is Nominatim free? The public instance is free for light use, with a 1 req/s limit and a mandatory User-Agent.

Why do I get 403? Your User-Agent is missing or generic — send a descriptive one identifying your app.

Can I use it commercially? Light use is fine; heavy or commercial use needs a Nominatim Data Use agreement or your own instance.