opacity property was introduced in CSS3 to enable developers to enable transparency in HTML elements.
opacity property allows you to specify a level of opacity against an object so that it becomes semi-transparent, or even fully transparent (if that's the desired effect).
Here are the possible values:
- Specifies the amount of transparency that should be applied to the element. A value of
0.0specifies fully transparent and a value of
1.0specifies fully opaque (no transparency).
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
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
- Applies To
- All elements
- Yes (see example)
Working Example within an HTML Document
opacityproperty is defined in CSS Color Module Level 3 (W3C Recommendation 07 June 2011).
opacity property isn't the only way to specify opacity/transparency in CSS. CSS3 provides for alpha colors, as well as the
transparent keyword. More about these below.
- Alpha Color Functions
CSS3 has introduced
hsla()color functions, which allow you to specify the opacity at the color level.
background-color: rgba(0,0,0,0.4)provides the color black (i.e.
0,0,0) with an opacity of 0.4. And for an HSLA example,
background-color: hsla(0, 100%, 50%, 0.8)specifies the color red (i.e.
0, 100%, 50%) with an opacity of 0.8.
transparentkeyword can be applied against any element when using the
transparentkeyword specifies that the element should be fully transparent. It is shorthand for
In CSS 1, the
transparentkeyword was limited to the
background-colorproperty. In CSS level 2, it was extended to the
border-colorproperty. In CSS 3, the
transparentkeyword has been extended to any element that uses the
The following table provided by Caniuse.com shows the level of browser support for this feature.
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.