Size vs ViewBox

The svg element can have attributes width and height in pixels to define the size of the image and it can have an attrbute called ViewBox.

width and height are the actual size of the image on the screen, the rendered size. (Well, assuming there are not external forces to change that.)

ViewBox is an internal coordinate system viewBox="X Y width height" where X, Y are the coordinates of the top-left corner and width and height are well, the dimensions of the coordinate system.

I think one should almost always use ViewBox.