repeating-radial-gradient()

This works similarly to the standard radial gradients as described by radial-gradient(), but it automatically repeats the color stops infinitely in both directions, with their positions shifted by multiples of the difference between the last color stop's position and the first one's position.

Like any other gradient, a repeating CSS radial gradient is not a CSS <color> but an image with no intrinsic dimensions; that is, it has no natural or preferred size, nor ratio. Its concrete size will match the one of the element it applies to.

Syntax

Definition of the ending shape
repeating-radial-gradient( circle, … )                /* Synonym of repeating-radial-gradient( circle farthest-corner, …) */
repeating-radial-gradient( ellipse, … )               /* Synonym of repeating-radial-gradient( ellipse farthest-corner, …) */
repeating-radial-gradient( <extent-keyword>, … )      /* It draws concentric circles */
repeating-radial-gradient( circle radius, … )         /* Concentrinc centered circles of the given length. It can't be in %. */
repeating-radial-gradient( ellipse x-axis y-axis, … ) /* The two semi-major axis are given, horizontal, then vertical */

Definition of the position of the shape
repeating-radial-gradient (… at <position>, … )

Definition of the color stops
repeating-radial-gradient (…, <color-stop>)
repeating-radial-gradient (…, <color-stop>, <color-stop>)

Values

<position>

A <position>, interpreted in the same way as background-position or transform-origin. If omitted, the default is center.

<angle>

An angle establishing the gradient line, which extends from the starting point at this angle; this is 0deg by default.

<shape>

The gradient's shape. This is one of circle (meaning that the gradient's shape is a circle with constant radius) or ellipse (meaning that the shape is an axis-aligned ellipse). The default value is ellipse.

<size>

The size of the gradient. This is one of the Size constants listed below.

<color-stop>

Representing a fixed color at a precise position, this value is composed by a <color> value, followed by an optional stop position (either a <percentage> or a <length> along the virtual gradient ray). A percentage of 0%, or a length of 0, represents the center of the gradient, the value 100% the intersection of the ending shape with the virtual gradient ray. Percentage values in-between. are linearily positioned on the gradient ray.

<extent-keyword>

Are keywords describing how big the ending shape must be. The possible keywords are:

Constant	Description
closest-side	The gradient's ending shape meets the side of the box closest to its center (for circles) or meets both the vertical and horizontal sides closest to the center (for ellipses).
closest-corner	The gradient's ending shape is sized so it exactly meets the closest corner of the box from its center.
farthest-side	Similar to closest-side, except the ending shape is sized to meet the side of the box farthest from its center (or vertical and horizontal sides).
farthest-corner	The gradient's ending shape is sized so it exactly meets the farthest corner of the box from its center.

Early drafts were defining to other keywords, cover and contain, synonyms of the standard farthest-corner and closest-side respectively. Do exclusively use the standard keyword as some implementations have dropped to older variants.

Formal syntax

repeating-radial-gradient( 
       [[ circle  || <length> ]                     [at <position>]? , | 
        [ ellipse || [<length> | <percentage> ]{2}] [at <position>]? , |
        [[ circle | ellipse ] || <extent-keyword> ] [at <position>]? , |
                                                     at <position>   ,    <color-stop> [ , <color-stop> ]+ )
        \---------------------------------------------------------------/\--------------------------------/
                  Contour, size and position of the ending shape               List of color stops  
    
where <extent-keyword> = closest-corner | closest-side | farthest-corner | farthest-side
  and <color-stop> = <color> [ <percentage> | <length> ]?

Size constants

Constant	Description
closest-side	The gradient's shape meets the side of the box closest to its center (for circles) or meets both the vertical and horizontal sides closest to the center (for ellipses).
closest-corner	The gradient's shape is sized so it exactly meets the closest corner of the box from its center.
farthest-side	Similar to closest-side, except the shape is sized to meet the side of the box farthest from its center (or vertical and horizontal sides).
farthest-corner	The gradient's shape is sized so it exactly meets the farthest corner of the box from its center.
contain	A synonym for closest-side.
cover	A synonym for farthest-corner.

Usage

Radial gradients also run along an axis. At each end point of the axis, a radius is specified. This can be imagined as creating two "circles", where for each circle the center is specified by the point and the radius is specified by the radius length. The gradient runs outwards from the circumference of the inner circle to the circumference of the outer circle.

Black & white

<div id="grad1">Black white</div>

div {
  display: block;
  width: 50%;
  height: 80px;
  border-color: #000000;
  padding: 10px;
}
#grad1 {
  background: -webkit-repeating-radial-gradient(black, black 5px, white 5px, white 10px);
  background: -moz-repeating-radial-gradient(black, black 5px, white 5px, white 10px);
  background: -ms-repeating-radial-gradient(black, black 5px, white 5px, white 10px);
  background: -o-repeating-radial-gradient(black, black 5px, white 5px, white 10px);
  background: repeating-radial-gradient(black, black 5px, white 5px, white 10px);
  text-shadow: 1px 1px 0pt black;
  color: white;
  border: 1px solid black;
  height:5.5em;
}

background: repeating-radial-gradient(black, black 5px, white 5px, white 10px);

Farthest-corner

<div id="grad1">Farthest-corner</div>

div {
  display: block;
  width: 50%;
  height: 80px;
  border-radius: 10px;
  border-color: #000000;
  padding: 10px;
}
#grad1 {
  background: -webkit-repeating-radial-gradient(ellipse farthest-corner, red, black 5%, blue 5%, green 10%);
  background: -moz-repeating-radial-gradient(ellipse farthest-corner, red, black 5%, blue 5%, green 10%);
  background: -ms-repeating-radial-gradient(ellipse farthest-corner, red, black 5%, blue 5%, green 10%);
  background: -o-repeating-radial-gradient(ellipse farthest-corner, red, black 5%, blue 5%, green 10%);
  background: repeating-radial-gradient(ellipse farthest-corner, red, black 5%, blue 5%, green 10%);
  text-shadow: 1px 1px 0pt blue;
  color: white;
  border: 1px solid black;
  height:5.5em;
}

background: repeating-radial-gradient(ellipse farthest-corner, red, black 5%, blue 5%, green 10%);

Specifications

Specification	Status	Comment
CSS Image Values and Replaced Content Module Level 3 The definition of 'repeating-radial-gradient()' in that specification.	Candidate Recommendation	Initial definition.

Browser compatibility

[1] Before Firefox 36, Gecko didn't apply gradient on the pre-multiplied color space, leading to shade of grey unexpectedly appearing when used with transparency. Since Firefox 42, the prefixed version of gradients can be disabled by setting layout.css.prefixes.gradients to false.

In addition to the unprefixed support, Gecko 44.0 (Firefox 44.0 / Thunderbird 44.0 / SeaMonkey 2.41) added support for a -webkit prefixed version of the function for web compatibility reasons behind the preference layout.css.prefixes.webkit, defaulting to false. Since Gecko 49.0 (Firefox 49.0 / Thunderbird 49.0 / SeaMonkey 2.46) the preference defaults to true.

See also

• Using gradients, repeating-linear-gradient(), radial-gradient()
• WebKit's original proposal: http://webkit.org/blog/175/introducing-css-gradients/
• MSDN library, gradient filter (reference doc)