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The CSS @supports at-rule lets authors detect support of CSS features directly in CSS.

The CSS at-rule @supports is part of the CSS Conditional Rules Module Level 3 Draft. It allows authors to condition rules based on whether particular property declarations are supported in CSS.

In other words @supports lets you detect browser support of CSS features directly in CSS. Modernizr is a well known library that detects features using JavaScript.

The operators and and or allows to chain the detection of several features.


An abstract example with the detection of support for display: flex (known as CSS Flexible Box Layout Module):

@supports (display: flex) {
  div {
    display: flex;

Chaining detection of several features using the operator and:

@supports (background: rgba(0,0,0,0.2)) and (opacity: 0.8) {
  body {
    background: rgba(0,0,0,0.2);

  div {
    opacity: 0.8;

To detect if an experimental feature is supported with vendor-prefixes the or operator might be helpful:

(This example does not include -o- and -ms- prefixes as neither Opera nor Microsoft supported a prefixed version of box-shadow.)

@supports (-webkit-box-shadow: 0 0 2px #000) or
          (   -moz-box-shadow: 0 0 2px #000) or
          (        box-shadow: 0 0 2px #000) {

  div {
    -webkit-box-shadow: 0 0 2px #000;
       -moz-box-shadow: 0 0 2px #000;
            box-shadow: 0 0 2px #000;


 Browser support for this feature is still pretty limited.

Related specifications

CSS Conditional Rules Module Level 3
Candidate Recommendation

See also

Related articles


External resources