ipapi.co vs Nominatim

ipapi.co geolocates an IP address and returns the result as JSON, XML, or YAML without requiring an API key for light use, though the no-key path is rate-limited and marketed by the vendor as a free trial rather than a permanent free tier. Paid subscriptions start at $15/month (or $12/month billed annually) for 60,000 lookups/month, scaling up to $399/month for 15 million/month.

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 policy states a stock HTTP-library User-Agent will not do). The public instance at nominatim.openstreetmap.org mainly exists to power the search bar on openstreetmap.org and runs on donated servers with very limited capacity: its usage policy caps requests at an absolute maximum of 1 per second, forbids autocomplete-style querying outright, and requires results to be cached on the caller's side. Bulk geocoding is restricted rather than banned — a smaller one-time task is permissible on a single thread and a single machine, with distributed scripts disallowed and anything running longer than a day capped at 4 requests per minute. The policy points larger users first at commercial third-party providers, and the largest at running their own Nominatim instance.