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opacity

The opacity CSS property sets the opacity of an element. Opacity is the degree to which content behind an element is hidden, and is the opposite of transparency.

Syntax

Values

<alpha-value>
A <number> in the range 0.0 to 1.0, inclusive, or a <percentage> in the range 0% to 100%, inclusive, 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, content behind the element can be seen).
1 (default value) The element is fully opaque (visually solid).

Description

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

Using opacity with a value other than 1 places the element in a new stacking context.

If you do not want to apply opacity to child elements, use the background property instead. For example:

background: rgba(0, 0, 0, 0.4);

Accessibility concerns

If text opacity is adjusted, it is important to ensure that the contrast ratio between the color of the text and the background the text is placed over is high enough that people experiencing low vision conditions will be able to read the content of the page.

Color contrast ratio is determined by comparing the luminosity of the opacity-adjusted text and background color values. In order to meet current Web Content Accessibility Guidelines (WCAG), a ratio of 4.5:1 is required for text content and 3:1 for larger text such as headings. Large text is defined as 18.66px and bold or larger, or 24px or larger.

Formal definition

Initial value 1.0
Applies to all elements
Inherited no
Computed value the specified value, clipped in the range [0,1]
Animation type a number

Formal syntax

<alpha-value>

where
<alpha-value> = <number> | <percentage>

Examples

Setting background opacity

HTML

<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>

CSS

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 */
}

Result

Setting opacity on hover

HTML

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

CSS

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;
}

Result

Specifications

Specification Status Comment
CSS Color Module Level 4
The definition of 'opacity' in that specification.
Working Draft Defines percentage opacity values.
CSS Color Module Level 3
The definition of 'opacity' in that specification.
Recommendation Initial definition

Browser compatibilityUpdate compatibility data on GitHub

Desktop
Chrome Edge Firefox Internet Explorer Opera Safari
opacity 1 12 1
1
1 — 3.5
Prefixed
Prefixed Implemented with the vendor prefix: -moz-
9 9 2
2
1.1 — 2
Prefixed
Prefixed Implemented with the vendor prefix: -khtml-
Support for percentage opacity values 78 79 70 No No No
Mobile
Android webview Chrome for Android Firefox for Android Opera for Android Safari on iOS Samsung Internet
opacity 1 18 4 10.1 1 1.0
Support for percentage opacity values 78 78 No No No 12.0

See also

© 2005–2020 Mozilla and individual contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/CSS/opacity