width
The width
CSS property specifies the width of an element. By default, the property defines the width of the content area. If box-sizing
is set to border-box
, however, it instead determines the width of the border area.
/* <length> values */
width: 300px;
width: 25em;
/* <percentage> value */
width: 75%;
/* Keyword values */
width: 25em border-box;
width: 75% content-box;
width: max-content;
width: min-content;
width: available;
width: fit-content;
width: auto;
/* Global values */
width: inherit;
width: initial;
width: unset;
Examples
預設值 | auto |
---|---|
Applies to | all elements but non-replaced inline elements, table rows, and row groups |
繼承與否 | no |
Percentages | refer to the width of the containing block |
Computed value | a percentage or auto or the absolute length |
Animation type | a length, percentage or calc(); |
Syntax
The width
property is specified as either:
- one of the following keyword values:
available
,min-content
,max-content
,fit-content
,auto
. - a
<length>
or a<percentage>
. This may optionally be followed by one of the following keywords:border-box
,content-box
.
Values
<length>
-
Defines the width as an absolute value.
<percentage>
-
Defines the width as a percentage of the containing block's width. If the width of the containing block depends on the width of the element, the resulting layout is undefined.
border-box
實驗性質-
If present, the preceding
<length>
or<percentage>
is applied to the element's border box. content-box
實驗性質-
If present, the preceding
<length>
or<percentage>
is applied to the element's content box. auto
-
The browser will calculate and select a width for the specified element.
fill
實驗性質-
Use the
fill-available
inline size orfill-available
block size, as appropriate to the writing mode. max-content
實驗性質-
The intrinsic preferred width.
min-content
實驗性質-
The intrinsic minimum width.
available
實驗性質-
The containing block width minus horizontal margin, border and padding.
fit-content
實驗性質-
The larger of: the intrinsic minimum width
- the smaller of the intrinsic preferred width and the available width
Formal syntax
width =
auto |
<length-percentage [0,∞]> |
min-content |
max-content |
fit-content( <length-percentage [0,∞]> ) |
<calc-size()> |
<anchor-size()>
<length-percentage> =
<length> |
<percentage>
<calc-size()> =
calc-size( <calc-size-basis> , <calc-sum> )
<anchor-size()> =
anchor-size( [ <anchor-element> || <anchor-size> ]? , <length-percentage>? )
<calc-size-basis> =
<intrinsic-size-keyword> |
<calc-size()> |
any |
<calc-sum>
<calc-sum> =
<calc-product> [ [ '+' | '-' ] <calc-product> ]*
<anchor-element> =
<dashed-ident>
<anchor-size> =
width |
height |
block |
inline |
self-block |
self-inline
<calc-product> =
<calc-value> [ [ '*' | '/' ] <calc-value> ]*
<calc-value> =
<number> |
<dimension> |
<percentage> |
<calc-keyword> |
( <calc-sum> )
<calc-keyword> =
e |
pi |
infinity |
-infinity |
NaN
範例
預設寬度
p.goldie {
background: gold;
}
<p class="goldie">The Mozilla community produces a lot of great software.</p>
像素和相對大小
.px_length {
width: 200px;
background-color: red;
color: white;
border: 1px solid black;
}
.em_length {
width: 20em;
background-color: white;
color: red;
border: 1px solid black;
}
<div class="px_length">Width measured in px</div>
<div class="em_length">Width measured in em</div>
百分比
.percent {
width: 20%;
background-color: silver;
border: 1px solid red;
}
<div class="percent">Width in percentage</div>
內容最大值
p.maxgreen {
background: lightgreen;
width: intrinsic; /* Safari/WebKit uses a non-standard name */
width: -moz-max-content; /* Firefox/Gecko */
width: -webkit-max-content; /* Chrome */
}
<p class="maxgreen">The Mozilla community produces a lot of great software.</p>
內容最小值
p.minblue {
background: lightblue;
width: -moz-min-content; /* Firefox */
width: -webkit-min-content; /* Chrome */
}
<p class="minblue">The Mozilla community produces a lot of great software.</p>
規範
Specification |
---|
CSS Box Sizing Module Level 4 # width-height-keywords |
CSS Box Sizing Module Level 4 # sizing-values |
瀏覽器相容性
BCD tables only load in the browser