<alpha-value>

The <alpha-value> CSS data type represents a value that can be either a <number> or a <percentage>, specifying the alpha channel or transparency of a color.

The value of an <alpha-value> is given as either a <number> or a <percentage>.

If given as a number, the useful range is 0 (fully transparent) to 1.0 (fully opaque), with decimal values in between; that is, 0.5 indicates that half of the foreground color is used and half of the background color is used. Values outside the range of 0 to 1 are permitted, but are clamped to like within the range 0 to 1.

If the alpha value is given as a percentage, 0% corresponds to fully transparent while 100% indicates fully opaque.

When animated, values of the <alpha-value> CSS data type are interpolated as real, floating-point numbers. The speed of the interpolation is determined by the timing function associated with the animation.

Here an alpha value is used to set partially transparent text:

/* <rgba()> */
color: rgba(34, 12, 64, 0.6);
color: rgba(34.0 12 64 / 60%);

Here an alpha value is used to determine which parts of an image are considered part of a shape:

/* shape-image-threshold */
shape-image-threshold: 70%;
shape-image-threshold: 0.7;

• Fundamental text and font styling
• CSS data types
• CSS Color
• <color>