The max-width property is used to set the maximum width of an item. Maximum width of element does not include css paddings, borders or margins. The max-height property allows you to specify the maximum content height of an element. This maximum height of element does not include css paddings, borders or margins.

The max-width css property define the maximum width of an element (box).
If the content box is larger than the css max width, it will automatically change the width