CSS overflow

The CSS overflow property is used for setting the clipping behavior on an element. It determines what to do when a box's contents are too large to fit inside. For example, you could specify that a box grows scroll bars whenever its contents get too large to fit inside. Alternatively, you could specify that the contents are simply hidden from view.

As of CSS3, the overflow property is a shorthand property for the overflow-x and overflow-y properties (this is because those properties were only introduced in CSS3). The overflow property allows you to set both of those properties at once. Therefore, the overflow property is a time-efficient and code-efficient way of setting your "overflow-related" properties.


Possible Values

The overflow property is shorthand, and accepts one or two keywords (below). If it has one keyword, that keyword sets both overflow-x and overflow-y; if it has two keywords, it sets overflow-x to the first and overflow-y to the second

Specifies that the content should not be clipped. In other words, it should be displayed outside the content box.
Specifies that the content is clipped (i.e. the parts that extend beyond the content box are hidden), and no scroll bars (or other scrolling mechanism) are supplied.
Specifies that the content box should provide scroll bars (or other scrolling mechanism) regardless of whether the content is clipped or not.
Specifies that the content box should provide scroll bars (or other scrolling mechanism) only when the content overflows (i.e. is too big to fit within the content box).

In addition, all CSS properties also accept the following CSS-wide keyword values as the sole component of their property value:

Represents the value specified as the property's initial value.
Represents the computed value of the property on the element's parent.
This value acts as either inherit or initial, depending on whether the property is inherited or not. In other words, it sets all properties to their parent value if they are inheritable or to their initial value if not inheritable.

Basic Property Information

Initial Value
See individual properties
Applies To

The exact wording depends on the spec:

  • CSS2: Block containers.
  • CSS basic box model: Non-replaced block-level elements and non-replaced 'inline-block' elements.
  • CSS Overflow Module Level 3: Block containers, flex containers, and grid containers.

Example Code

Basic CSS

Working Example within an HTML Document

Try it

CSS Specifications

Vendor Prefixes

For maximum browser compatibility many web developers add browser-specific properties by using extensions such as -webkit- for Safari, Google Chrome, and Opera (newer versions), -ms- for Internet Explorer, -moz- for Firefox, -o- for older versions of Opera etc. As with any CSS property, if a browser doesn't support a proprietary extension, it will simply ignore it.

This practice is not recommended by the W3C, however in many cases, the only way you can test a property is to include the CSS extension that is compatible with your browser.

The major browser manufacturers generally strive to adhere to the W3C specifications, and when they support a non-prefixed property, they typically remove the prefixed version. Also, W3C advises vendors to remove their prefixes for properties that reach Candidate Recommendation status.

Many developers use Autoprefixer, which is a postprocessor for CSS. Autoprefixer automatically adds vendor prefixes to your CSS so that you don't need to. It also removes old, unnecessary prefixes from your CSS.

You can also use Autoprefixer with preprocessors such as Less and Sass.