CSS Box Model
CSS Box Model is a module of CSS that defines the rectangular boxes—including their padding and margin—that are generated for elements and laid out according to the visual formatting model.
The Box Model
A box in CSS consists of a content area, which is where any text, images, or other HTML elements are displayed. This is optionally surrounded by padding, a border, and a margin, on one or more sides. The box model describes how these elements work together to create a box as displayed by CSS. To learn more about it read Introduction to the CSS Box Model.
Box-edge keywords
The Box Model specification defines a set of keywords that refer to the edges of each part of the box, these are used as keyword values in CSS including as a value for the box-sizing
property, to control how the box model calculates its size.
content-box
-
The edge of the content area of the box.
padding-box
-
The edge of the padding of the box, if there is no padding on a side then this is the same as
content-box
. border-box
-
The edge of the border of the box, if there is no border on a side then this is the same as
padding-box
. margin-box
-
The edge of the margin of the box, if there is no margin on a side then this is the same as
border-box
. stroke-box
-
In SVG refers to the stroke bounding box, in CSS treated as
content-box
. view-box
-
In SVG refers to the nearest SVG viewport element's origin box, which is a rectangle with the width and height of the initial SVG user coordinate system established by the
viewBox
attribute for that element. In CSS treated asborder-box
.
Reference
Properties
Note: This specification defines the physical padding and margin properties. Flow-relative properties, which relate to text direction, are defined in Logical Properties and Values.
Properties controlling the margins of a box
Margins surround the border edge of a box, and provide spacing between boxes.
Properties controlling the paddings of a box
Padding is inserted between the content edge and border edge of a box.
Other properties
There are other properties that relate to the box model, that are defined elsewhere.
Guides
- Introduction to the CSS box model
-
Explains one of the fundamental concept of CSS: the box model. This model defines how CSS lays out elements, including their content, padding, border, and margin areas.
- Mastering margin collapsing
-
Sometimes, two adjacent margins are collapsed into one. This article describes the rules that govern when and why this happens, and how to control it.
- Visual formatting model
-
Explains the visual formatting model.
Specifications
Specification |
---|
CSS Box Model Module Level 3 |