how foursquare determine a user location?

Question

I just use foursquare first time, looks it find my location and shows on the map very correct. I am using desktop at home, just curious, how does it know my address? Thanks.

Answer 1

It uses the GPS from your phone and updates your position on that.

For an exact businesses you are at, you "Check-In" to a business through the app.

Answer 2

It uses HTML5's Geolocation API to determine a user's location