Building a Compass in the Browser: How the DeviceOrientation API Actually Works

Pull up any browser-based compass tool on your phone and it works instantly — no app install, no native code. That's not a trick; it's a real browser API doing real sensor fusion under the hood. Here's what's actually happening between "grant motion permission" and a needle pointing north. The API: DeviceOrientationEvent Browsers expose device orientation through the DeviceOrientationEvent, which fires continuously as the device moves and gives you three angles: window.addEventListener('deviceor