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css function

`blur()` CSS function

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The blur() CSS function applies a Gaussian blur to the input image. Its result is a filter-function.

Interactive exampleOpen the canonical MDN source to run this embedded demo.
filter: blur(0);

filter: blur(4px);

filter: blur(1.5rem);

<section id="default-example">
  <img
    class="transition-all"
    id="example-element"
    src="/shared-assets/images/examples/firefox-logo.svg"
    width="200" />
</section>

Syntax

blur()         /* No effect */
blur(0)        /* No effect */

blur(8px)      /* Blur with 8px radius */
blur(1.17rem)  /* Blur with 1.17rem radius */

Parameters

  • length Optional
    • : Specifies the radius of the blur. It defines the value of the standard deviation to the Gaussian function, that is, how many pixels on the screen blend into each other. Therefore, a larger value will create more blur. A value of 0 leaves the input unchanged. The initial value for interpolation is 0. Percentage values are invalid. The default value is 0.

SVG filter

The SVG <feGaussianBlur> filter element can also be used to blur content. The filter’s stdDeviation attribute accepts up to two values enabling creating more complex blur values. To create an equivalent blur, we include one value for stdDeviation. This SVG effect can then be referenced by ID:

<svg role="none">
  <filter id="blur11">
    <feGaussianBlur stdDeviation="1.1" edgeMode="duplicate" />
  </filter>
</svg>

The following declarations produce the same effect:

filter: blur(1.1px);
filter: url("#blur11"); /* with embedded SVG */
filter: url("folder/fileName.svg#blur11"); /* external svg filter definition */

Formal syntax

Examples

This example shows three images: the image with a blur() filter function applied, the image with the equivalent SVG blur function applied, and the original images for comparison:

.filter {
  filter: blur(3.5px);
}

<svg role="img" aria-label="Flag">
  <filter id="blur">
    <feGaussianBlur stdDeviation="3.5" edgeMode="duplicate" />
  </filter>
  <image
    href="https://mdn.github.io/shared-assets/images/examples/progress-pride-flag.jpg"
    xlink:href="https://mdn.github.io/shared-assets/images/examples/progress-pride-flag.jpg"
    filter="url('#blur')" />
</svg>

svg:not([height]) {
  display: none;
}

th,
td {
  padding: 5px;
}

<table>
  <thead>
    <tr>
      <th>Live example</th>
      <th>SVG Equivalent</th>
      <th>Original image</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>
        <img
          class="filter"
          src="https://mdn.github.io/shared-assets/images/examples/progress-pride-flag.jpg"
          alt="Pride flag" />
      </td>
      <td>
        <svg id="svg" height="220" width="220" overflow="visible">
          <filter id="svgBlur">
            <feGaussianBlur stdDeviation="3.5" />
          </filter>
          <image
            href="https://mdn.github.io/shared-assets/images/examples/progress-pride-flag.jpg"
            xlink:href="https://mdn.github.io/shared-assets/images/examples/progress-pride-flag.jpg"
            filter="url('#svgBlur')" />
        </svg>
      </td>
      <td>
        <img
          src="https://mdn.github.io/shared-assets/images/examples/progress-pride-flag.jpg"
          alt="Pride flag" />
      </td>
    </tr>
  </tbody>
</table>
Interactive exampleOpen the canonical MDN source to run this embedded demo.

Specifications

SpecificationsStandards references are available on the canonical MDN page.

Browser compatibility

Browser compatibilityCompatibility data is available on the canonical MDN page.

See also