When you tap “Start Workout”, your browser asks for camera permission and shows the video right here on the page — it stays on your phone or computer. A pose-detection model runs entirely inside your browser, on your device's own processor, reading the camera frames and turning your body into a handful of moving points that track your joints. Only those points are used to count your reps. The frames themselves aren't uploaded and no server receives them. Traffic flows one way: the page and the small detection model are downloaded to your device, and nothing from your camera is sent back.