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css module

CSS backgrounds and borders

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The CSS backgrounds and borders module provides properties for adding backgrounds, borders, rounded corners, and box shadows to elements.

You can add different types of border styles, including borders made of images of any image type, from raster images to CSS gradients. Borders can be square or rounded, and a different radius can be set for each corner. Elements can be rounded whether or not they have a visible border.

Box shadows include inset and outset shadow, single or multiple shadows, and solid or allowed to fade to transparent. An outer box-shadow casts a shadow as if the border-box of the element were opaque. An inner box-shadow casts a shadow as if everything outside the padding edge were opaque. The shadow can be solid or include a spread distance with the shadow color transitioning to transparent.

The properties in this module also let you define whether cells inside a <table> should have shared or separate borders.

Backgrounds, borders, and box shadows in action

This sample of borders, backgrounds, and box shadows consists of centered background images made of linear and radial gradients. A series of box shadows make the border appear to “pop”. The element on the left has a border image set. The element on the right has a rounded dotted border.

<article>
  <div></div>
  <div></div>
</article>

article {
  display: flex;
  gap: 10px;
}
div {
  color: #58ade3;
  height: 320px;
  width: 240px;
  padding: 20px;
  margin: 10px;
  border: dotted 15px; /* defaults to `currentColor` */
  border-radius: 100px 0;
  background-image:
    radial-gradient(
      circle,
      transparent 60%,
      currentColor 60% 70%,
      transparent 70%
    ),
    linear-gradient(45deg, currentColor, white),
    linear-gradient(transparent, transparent);
  /* the third transparent background image was added to provide space for the background color to show through */
  background-color: currentColor;
  background-position: center;
  background-size:
    60px 60px,
    120px 120px;
  background-clip: content-box, content-box, padding-box;
  box-shadow:
    inset 5px 5px 5px rgb(0 0 0 / 0.4),
    inset -5px -5px 5px rgb(0 0 0 / 0.4),
    5px 5px 5px rgb(0 0 0 / 0.4),
    -5px -5px 5px rgb(0 0 0 / 0.4);
}
div:first-of-type {
  border-radius: 0;
  border-image-source: repeating-conic-gradient(
    from 3deg at 25% 25%,
    currentColor 0 3deg,
    transparent 3deg 6deg
  );
  border-image-slice: 30;
}
Interactive exampleOpen the canonical MDN source to run this embedded demo.

The background images are defined with background-image. The images are centered with background-position. Different values of the background-clip property for the multiple background images are used to make the background images stay within the content box. The background color gets clipped to the padding box preventing the background from appearing through the transparent sections for the border-image and the dotted border. The rounded corners in the element on the right are created using the border-radius property. A single box-shadow declaration is used to set all the shadows, both inset and outset.

Reference

Properties

The CSS backgrounds module level 4 also introduces the background-position-block, background-position-inline, background-repeat-block, background-repeat-inline, and background-tbd properties. Currently, no browsers support these features.

Data types

Guides

Specifications

SpecificationsStandards references are available on the canonical MDN page.

See also