overflow - CSS: Cascading Style Sheets 编辑

The overflow CSS shorthand property sets the desired behavior for an element's overflow — i.e. when an element's content is too big to fit in its block formatting context — in both directions.

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Constituent properties

This property is a shorthand for the following CSS properties:

• overflow-x
• overflow-y

Syntax

/* Keyword values */
overflow: visible;
overflow: hidden;
overflow: clip;
overflow: scroll;
overflow: auto;
overflow: hidden visible;

/* Global values */
overflow: inherit;
overflow: initial;
overflow: unset;

The overflow property is specified as one or two keywords chosen from the list of values below. If two keywords are specified, the first applies to overflow-x and the second to overflow-y. Otherwise, both overflow-x and overflow-y are set to the same value.

Values

visible

Content is not clipped and may be rendered outside the padding box.

hidden

Content is clipped if necessary to fit the padding box. No scrollbars are provided, and no support for allowing the user to scroll (such as by dragging or using a scroll wheel) is allowed. The content can be scrolled programmatically (for example, by setting the value of a property such as offsetLeft), so the element is still a scroll container.

clip

Like for hidden, the content is clipped to the element's padding box. The difference between clip and hidden is that the clip keyword also forbids all scrolling, including programmatic scrolling. The box is not a scroll container, and does not start a new formatting context. If you wish to start a new formatting context, you can use display: flow-root to do so.

scroll

Content is clipped if necessary to fit the padding box. Browsers always display scrollbars whether or not any content is actually clipped, preventing scrollbars from appearing or disappearing as content changes. Printers may still print overflowing content.

auto

Depends on the user agent. If content fits inside the padding box, it looks the same as visible, but still establishes a new block formatting context. Desktop browsers provide scrollbars if content overflows.

overlay

Behaves the same as auto, but with the scrollbars drawn on top of content instead of taking up space. Only supported in WebKit-based (e.g., Safari) and Blink-based (e.g., Chrome or Opera) browsers.

Mozilla extensions

-moz-scrollbars-none [1]

Use overflow: hidden instead.

-moz-scrollbars-horizontal [1]

Use overflow-x: scroll and overflow-y: hidden, or overflow: hidden scroll instead.

-moz-scrollbars-vertical [1]

Use overflow-x: hidden and overflow-y: scroll, or overflow: scroll hidden instead.

-moz-hidden-unscrollable

Use overflow: clip instead.

[1] As of Firefox 63, this feature is behind a feature preference setting. In about:config, set layout.css.overflow.moz-scrollbars.enabled to true

Description

Overflow options include clipping, showing scrollbars, or displaying the content flowing out of its container into the surrounding area.

Specifying a value other than visible (the default) creates a new block formatting context. This is necessary for technical reasons — if a float intersected with the scrolling element it would forcibly rewrap the content after each scroll step, leading to a slow scrolling experience.

In order for overflow to have an effect, the block-level container must have either a set height (height or max-height) or white-space set to nowrap.

Setting one axis to visible (the default) while setting the other to a different value results in visible behaving as auto.

The JavaScript Element.scrollTop property may be used to scroll an HTML element even when overflow is set to hidden.

Formal definition

Formal syntax

[ visible | hidden | clip | scroll | auto ]{1,2}

Examples

Setting different overflow values for text

p {
  width: 12em;
  height: 6em;
  border: dotted;
  overflow: visible; /* content is not clipped */
}

visible (default)
Sed ut perspiciatis unde omnis iste natus error sit voluptatem accusantium doloremque laudantium.

p { overflow: hidden; /* no scrollbars are provided */ }

overflow: hidden
Sed ut perspiciatis unde omnis iste natus error sit voluptatem accusantium doloremque laudantium.

p { overflow: scroll; /* always show scrollbars */ }

overflow: scroll
Sed ut perspiciatis unde omnis iste natus error sit voluptatem accusantium doloremque laudantium.

p { overflow: auto; /* append scrollbars if necessary */ }

overflow: auto
Sed ut perspiciatis unde omnis iste natus error sit voluptatem accusantium doloremque laudantium.

Specifications

Browser compatibility

BCD tables only load in the browser

See also

• Related CSS properties: text-overflow, white-space, overflow-x, overflow-y, overflow-inline, overflow-block, clip, display
• CSS Overflow and Debug scrollable overflow