When working with views and trying to configure the layout for an application, it’s important to know the difference between a view’s bounds and frames. Many developers get confused between the frame and bounds and when they should use the two properties. The main reason is because many developers do not know the difference between the two. So, in order to understand the difference, let’s understand the definition and properties of a view.

The bounds of a UIView is the rectangle, expressed as a location (x,y) and size (width, height) relative to its own coordinate system (0,0).

The frame of a UIView is the rectangle, expressed as a location (x,y) and size (width, height) relative to the superview it is contained within.

Let me give you an example of this two from our day to day lives.

For frame, I think of a picture frame on a wall. The picture frame is like the border of a view. I can hang the picture anywhere I want on the wall. In the same way, I can put a view anywhere I want inside a parent view (also called a superview). The parent view is like the wall. The origin of the coordinate system in iOS is the top left. We can put our view at the origin of the superview by setting the view frame's x-y coordinates to (0, 0), which is like hanging our picture in the very top left corner of the wall. To move it right, increase x, to move it down increasingy.(image)

For bounds, I think of a basketball court where sometimes the basketball gets knocked out of bounds. You are dribbling the ball all over the basketball court, but you don't really care where the court itself is. It could be in a gym, or outside at a high school, or in front of your house. It doesn't matter. You just want to play basketball. In the same way, the coordinate system for a view's bounds only cares about the view itself. It doesn't know anything about where the view is located in the parent view. The bounds' origin (point (0, 0) by default) is the top left corner of the view. Any subviews that this view has are laid out in relation to this point. It is like taking the basketball to the front left corner of the court.(image)

Now the confusion comes when to use what ?

Since frame relates a view's location in its parent view, you use it when you are making outward changes, like changing its width or finding the distance between the view and the top of its parent view.

Use the bounds when you are making inward changes, like drawing things or arranging subviews within the view. Also use the bounds to get the size of the view if you have done some transfomation on it.