CSS Feature Queries

Feature queries let you ask the browser, directly in CSS, if it supports a feature. You write a condition using the @supports keyword, and the rules inside the block only apply when the test passes. They are a well supported part of CSS.

Why do feature queries exist?

CSS already has a fallback mechanism: when a browser meets a declaration it does not understand, it ignores that single line and moves on.

That works for one property. It does not work when a whole layout depends on a feature.

Think about CSS Grid. If the browser supports it, you want one set of rules. If it doesn’t, you want a different layout, maybe based on Flexbox. Feature queries let you group those rules and apply them all together, or not at all.

How to write a feature query

You wrap a property and value pair in parentheses after @supports:

@supports (display: grid) {
  .gallery {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
  }
}

We check if the browser supports the grid value for the display property. If it does, the rules inside the block apply.

You can use @supports for any CSS property, to check any value:

@supports (position: sticky) {
  .site-header {
    position: sticky;
    top: 0;
  }
}

Combining conditions

We can use the logical operators and, or and not to build complex feature queries.

This example checks if the browser supports both CSS Grid and Flexbox:

@supports (display: grid) and (display: flex) {
  /* apply this CSS */
}

With not you can target browsers that lack a feature, and give them a fallback layout:

@supports not (display: grid) {
  .gallery {
    display: flex;
    flex-wrap: wrap;
  }
}

A common mistake

Each condition needs its own parentheses, with both the property and the value inside.

This is invalid, and the browser ignores the entire block:

@supports display: grid {
  /* never applied */
}

Write @supports (display: grid) instead.

One more thing to keep in mind. Put your base styles outside the query, and only the enhancements inside. A really old browser that doesn’t understand @supports at all skips the whole block, so the page must still work without it.