opacity

Summary

The opacity CSS property specifies the transparency of an element, that is, the degree to which the background behind the element is overlaid.

The value applies to the element as a whole, including its contents, even though the value is not inherited by child elements. Thus, an element and its contained children all have the same opacity relative to the element's background, even if the element and its children have different opacities relative to one another.

Using this property with a value different than 1 places the element in a new stacking context.

• Initial value 1.0
• Applies to all elements
• Inherited no
• Media visual
• Computed value the specified value, clipped in the range [0,1]
• Animatable yes, as a number
• Canonical order the unique non-ambiguous order defined by the formal grammar

Syntax

Formal syntax: <number>

opacity: 1
opacity: 1.0
opacity: 0.6
opacity: 0.0
opacity: 0

opacity: inherit

Values

<number>

Is a <number> in the range 0.0 to 1.0, both included, representing the opacity of the channel, that is the value of its alpha channel. Any value outside the interval, though valid, is clamped to the nearest limit in the range.

Value	Meaning
0	The element is fully transparent (that is, invisible).
Any <number> strictly between 0 and 1	The element is translucent (that is, background can be seen).
1	The element is fully opaque (solid).

Examples

Basic example

div { background-color: yellow; }
.light {
  opacity: 0.2; /* Barely see the text over the background */
}
.medium {
  opacity: 0.5; /* See the text more clearly over the background */
}
.heavy {
  opacity: 0.9; /* See the text very clearly over the background */
}

<div class="light">You can barely see this.</div>
<div class="medium">This is easier to see.</div>
<div class="heavy">This is very easy to see.</div>

Different opacity with :hover

img.opacity {
  opacity: 1;
  filter: alpha(opacity=100); /* IE8 and lower */
  zoom: 1; /* Triggers "hasLayout" in IE 7 and lower */
}
 
img.opacity:hover {
  opacity: 0.5;
  filter: alpha(opacity=50);
  zoom: 1;
}

<img src="//developer.mozilla.org/media/img/mdn-logo.png"
     alt="MDN logo" width="128" height="146"
     class="opacity">

Specifications

Browser compatibility

• History: Prior to Mozilla 1.7 (Firefox 0.9) the -moz-opacity property was implemented in a non-standard (inherited) way. With Firefox 0.9 the behavior changed and the property was renamed to opacity. Since then -moz-opacity was supported just as an alias for opacity.
• Gecko 1.9.1 (Firefox 3.5) and later do not support -moz-opacity and support for MozOpacity in javascript was removed in Gecko 13. By now, you should be using simply opacity.
• Prior to version 9, Internet Explorer does not support opacity, rather it supports filter instead.
• IE4 to IE9 supported the extended form progid:DXImageTransform.Microsoft.Alpha(Opacity=xx).
• IE8 introduced -ms-filter, which is synonymous with filter. Both are gone in IE10
• Similar to -moz-opacity, -khtml-opacity has been dead since early 2004 (release of Safari 1.2).
  Konqueror never had support for -khtml-opacity and had been supporting opacity since version 4.0.

See also

• MSDN Microsoft's filter:alpha(opacity=xx)