The rgb() functional notation expresses a color according to its red, green, and blue components. An optional alpha component represents the color's transparency.


CSS Colors Level 4 made some changes to rgb(). In browsers that support the standard rgba() is an alias for rgb(), they accept the same parameters and behave the same way.

The Level 4 specification also allows for space-separated in addition to comma-separated values.


rgb(255,255,255) /* white */
rgb(255,255,255,.5) /* white with 50% opacity */
rgb(255 255 255); /* CSS Colors 4 space-separated values */


Functional notation: rgb[a](R, G, B[, A])
R (red), G (green), and B (blue) can be either <number>s or <percentage>s, where the number 255 corresponds to 100%. A (alpha) can be a <number> between 0 and 1, or a <percentage>, where the number 1 corresponds to 100% (full opacity).
Functional notation: rgb[a](R G B[ / A])
CSS Colors Level 4 adds support for space-separated values in the functional notation.

Browser compatibility

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Space-separated values

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Accepts alpha value

BCD tables only load in the browser