What is the difference between frame and bounds in UIView?

frame and bounds are both CGRect properties of UIView but use different coordinate systems: frame: the view's size and position in its superview's coordinate system. The origin is relative to the superview: view.frame = CGRect(x: 20, y: 50, width: 200, height: 100) // Positioned at (20, 50) in superview. bounds: the view's size and position in its own coordinate system. The origin is usually (0, 0) unless scrolled: view.bounds // Usually CGRect(x: 0, y: 0, width: 200, height: 100). Key difference — when they diverge: If you rotate a view using a transform, the frame changes (it's the smallest bounding rectangle in superview coords) but bounds stays the same: view.transform = CGAffineTransform(rotationAngle: .pi / 4) // 45 degrees print(view.frame) // Larger bounding box around the rotated view print(view.bounds) // Still the view's own rect. UIScrollView bounds: bounds.origin changes as the user scrolls — this is how scrolling works. The contentOffset IS the bounds.origin: scrollView.bounds.origin.y == scrollView.contentOffset.y. Rules: use frame to position a view within its superview; use bounds to draw inside a view (CGContext uses bounds); use frame.size and bounds.size — they should be equal for non-transformed views; frame.origin and bounds.origin differ for transformed views. center: view.center = CGPoint(x: superview.bounds.midX, y: superview.bounds.midY) — centers in superview.