CSS Box Sizing is a feature that allows you to control the size and dimensions of HTML elements. It gives you the ability to specify how the size of an element is calculated, including the width, height, padding, and border. With CSS Box Sizing, you can make sure that
In web development, the CSS box model refers to how HTML elements are modeled in browser engines and how the dimensions of those HTML elements are derived from CSS properties. It is a fundamental concept for the composition of HTML webpages. The guidelines of the box model are described by web standards World Wide Web Consortium (W3C) specifically the CSS Working Group. For much of the late-1990s and early 2000s there had been non-standard compliant implementations of the box model in mainstream browsers. With the advent of CSS2 in 1998, which introduced the box-sizing property, the problem had mostly been resolved.