Geolocation API is a W3C browser interface, reached through navigator.geolocation, that returns a device's latitude, longitude and accuracy radius once the user allows it. It only works in secure contexts, so a page served over plain HTTP gets a denial. The W3C specification became a Recommendation on 1 September 2022 and returned to Candidate Recommendation in March 2026. The number people search for is accuracy, which is a radius in meters at 95% confidence.
The API has three methods on navigator.geolocation: getCurrentPosition() for a single fix, watchPosition() for repeated updates that returns a numeric watch ID, and clearWatch() to stop one. Each takes a success callback, an optional error callback and an optional options object. The browser shows a permission prompt the first time, and the permission can be denied or revoked at any time.
A successful call hands you a GeolocationPosition with a timestamp and a coords object. The coords fields are:
The options object has three members. enableHighAccuracy defaults to false and is only a hint, and the spec warns it can slow responses. timeout is in milliseconds and defaults to 4294967295 (0xFFFFFFFF), which in practice means wait forever. maximumAge is in milliseconds and defaults to 0, meaning no cached position is accepted. The time spent waiting for the permission prompt does not count against timeout.
Failures arrive as a GeolocationPositionError with code 1 (PERMISSION_DENIED), 2 (POSITION_UNAVAILABLE) or 3 (TIMEOUT).
The sample below uses a hand-written coordinates object, because Node has no geolocation. It measures the great-circle distance to a target with the haversine formula and compares it to accuracy.
const coords = { latitude: 48.8584, longitude: 2.2945, accuracy: 25 };
const target = { latitude: 48.8606, longitude: 2.3376 };
const R = 6371008.8; // mean Earth radius in meters
const rad = d => d * Math.PI / 180;
function haversine(a, b) {
const dLat = rad(b.latitude - a.latitude), dLon = rad(b.longitude - a.longitude);
const h = Math.sin(dLat / 2) ** 2 +
Math.cos(rad(a.latitude)) * Math.cos(rad(b.latitude)) * Math.sin(dLon / 2) ** 2;
return 2 * R * Math.asin(Math.sqrt(h));
}
const d = haversine(coords, target);
console.log(Math.round(d) + " m");
console.log(d > coords.accuracy ? "outside the 95% accuracy circle" : "inside the accuracy circle");Output:
3163 m
outside the 95% accuracy circleThe accuracy value is the radius, in meters, of a circle around the reported coordinates that contains the true position with 95% confidence. A value of 25 means the device is probably within 25 m, not exactly at the point. Treat the position as a circle, not a pin, and ignore results whose accuracy is too coarse for your use.