nominatim.reverse

beta Standard

Reverse geocoding of a coordinate to the nearest address.

GET /v1/nominatim/reverse

What you get#

One Nominatim record in Onekey's unified shape, in data. If the record does not exist you get a 404 not_found and are not charged.

What it costs#

Standard · 1 credit for a fresh fetch, charged only when it succeeds.
Free when served from cache (0.2 credit for a cached response over 100 KB).
Free if the request is invalid (never charged) or the source fails or reports not found (refunded).

Parameters#

Name	Type	Required	Default	What it is	Constraints
`lat`	string	yes	(required)	Latitude in decimal degrees (-90..90)	max 10 chars; must match `-?(?:[0-8]?\d(?:\.\d{1,6})?\|90(?:\.0{1,6})?)`; trimmed
`lon`	string	yes	(required)	Longitude in decimal degrees (-180..180)	max 11 chars; must match `-?(?:1[0-7]\d(?:\.\d{1,6})?\|\d{1,2}(?:\.\d{1,6})?\|180(?:\.0{1,6})?)`; trimmed
`zoom`	string	no	`18`	Detail level (3=country .. 18=building)	max 2 chars; must match `\d\|1[0-8]`; trimmed

Request#

curl "https://api.onekey.dev/v1/nominatim/reverse?lat=52.52&lon=13.41" \
  -H "x-api-key: YOUR_API_KEY"

Try it

Add your key to run this call right here. No key? Get one free. The key stays in this tab.

Recorded response#

A real Nominatim response, recorded and returned in Onekey's shape. Fields the platform does not provide are null.

json

{
  "success": true,
  "data": {
    "entity": {
      "id": "145530022",
      "name": "Klosterviertel, Spandauer Vorstadt, Mitte, Berlin, 10178, Deutschland",
      "category": "highway",
      "description": "pedestrian"
    },
    "place": {
      "lat": 52.5200175,
      "lon": 13.410084
    },
    "ext": {
      "importance": 0.05342208819714653,
      "osmType": "way",
      "osmId": "1425774289"
    }
  },
  "metadata": {
    "platform": "nominatim",
    "endpoint": "reverse",
    "cached": false,
    "stale": false,
    "age_s": 0,
    "fetched_at": "2026-01-01T12:00:00+00:00",
    "credits_charged": 1,
    "request_id": "7f3a9c2e5b1d4c8fa2e6d0b9c4f18e37"
  },
  "error": null
}

Field mapping#

How this endpoint's source fields become Onekey's unified schema. Fields the source lacks come back as null.

Source path	Onekey field	Transform
`place_id`	`entity.id`	`toString`
`display_name`	`entity.name`	-
`category`	`entity.category`	-
`type`	`entity.description`	-
`lat`	`place.lat`	`toNumber`
`lon`	`place.lon`	`toNumber`
`importance`	`ext.importance`	`toNumber`
`osm_type`	`ext.osmType`	-
`osm_id`	`ext.osmId`	`toString`

Caching and freshness#

Fresh for about 30 minutes. Repeat calls in that window are served from cache and are free.
Between 30 minutes and 6 hours the cached copy is still served instantly and marked stale: true while Onekey refreshes it in the background.
If the source is down when a refresh is needed, the last copy can be served for up to 1 day more (marked stale).
A "not found" is remembered for 5 minutes and is free.
The cache is shared across all customers, which is what keeps repeat calls cheap.

What can go wrong#

Status	Code	What to do
401	`unauthorized`	Check the `x-api-key` header.
402	`insufficient_credits`	Add credits; your balance must cover the price.
404	`not_found`	That record does not exist. Free; do not retry.
422	`invalid_params`	Fix the parameters using the table above. Free.
429	`rate_limited`	Wait `Retry-After` seconds, then retry.
502	`upstream_error`	The source failed. Refunded; retry with backoff.

See Errors for the full list and retry guidance.

Status: beta (not yet verified against the live source).