break-before - CSS（层叠样式表） 编辑

The break-before CSS 属性定义页面，列或区域在生成的盒子之前应如何处理中断。 如果没有生成的盒子，则忽略该属性。

/* Generic break values */
break-before: auto;
break-before: avoid;

/* Page break values */
break-before: avoid-page;
break-before: page;
break-before: always;
break-before: left;
break-before: right;
break-before: recto;
break-before: verso;

/* Column break values */
break-before: avoid-column;
break-before: column;

/* Region break values */
break-before: avoid-region;
break-before: region;

/* Global values */
break-before: inherit;
break-before: initial;
break-before: unset;

Each possible break point (in other words, each element boundary) is affected by three properties: the break-after value of the previous element, the break-before value of the next element, and the break-inside value of the containing element.

To determine if a break must be done, the following rules are applied:

1. If any of the three concerned values is a forced break value (always, left, right, page, column, or region), it has precedence. If more than one of them are such a break, the one of the element that appears the latest in the flow is taken (i.e., the break-before value has precedence over the break-after value, which itself has precedence over the break-inside value).
2. If any of the three concerned values is an avoid break value (avoid, avoid-page, avoid-region, or avoid-column), no such break will be applied at that point.

Once forced breaks have been applied, soft breaks may be added if needed, but not on element boundaries that resolve in a corresponding avoid value.

初始值	auto
适用元素	block-level elements
是否是继承属性	否
计算值	as specified
Animation type	discrete

Syntax

The break-before property is specified as one of the keyword values from the list below.

Values

General break values

auto

Allows, but does not force, any break (page, column, or region) to be inserted right before the principal box.

avoid

Avoids any break (page, column, or region) from being inserted right before the principal box.

Page break values

avoid-page

Avoids any page break right before the principal box.

page

Forces a page break right before the principal box.

always

Forces a page break right before the principal box. (This is an alias of page, and has been kept to facilitate the transition from page-break-after, which is a subset of this property.)

left

Forces one or two page breaks right before the principal box, whichever will make the next page into a left page.

right

Forces one or two page breaks right before the principal box, whichever will make the next page into a right page.

recto

Forces one or two page breaks right before the principal box, whichever will make the next page into a recto page. (A recto page is a right page in a left-to-right spread or a left page in a right-to-left spread.)

verso

Forces one or two page breaks right before the principal box, whichever will make the next page into a verso page. (A verso page is a left page in a left-to-right spread or a left right in a right-to-left spread.)

Column break values

avoid-column

Avoids any column break right before the principal box.

column

Forces a column break right before the principal box.

Region break values

avoid-region

Avoids any region break right before the principal box.

region

Forces a region break right before the principal box.

Formal syntax

auto | avoid | always | all | avoid-page | page | left | right | recto | verso | avoid-column | column | avoid-region | region

Specifications

Specification	Status	Comment
CSS Fragmentation Module Level 3 break-before	Candidate Recommendation	Adds the recto and verso keywords. Changes the media type of this property from paged to visual. Defines the breaking algorithm with different kinds of breaks.
CSS Regions Module Level 1 break-before	Working Draft	Extends the property to handle region breaks. Adds the avoid-region and region keywords.
CSS Multi-column Layout Module break-before	Working Draft	Initial definition. Extends the CSS 2.1 page-break-before property to handle both page and column breaks.

Browser compatibility

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The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.