# CSS: Unrecognized at-rule “@view-transition”

> Canonical HTML version: https://rocketvalidator.com/html-validation/css-unrecognized-at-rule-view-transition
> Attribution: Rocket Validator (https://rocketvalidator.com)
> License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/)

The `@view-transition` at-rule is valid CSS but is not yet recognized by the W3C CSS validator because it is a relatively new feature defined in the CSS View Transitions Module Level 2 specification.

The `@view-transition` at-rule opts a document into cross-document view transitions when navigating between two same-origin pages. It is placed in the CSS of the destination page (the page being navigated to) and accepts a `navigation` descriptor that controls when the transition activates.

```css
@view-transition {
  navigation: auto;
}
```

The `navigation` descriptor accepts these values:

- `none` — no cross-document view transition occurs (default).
- `auto` — the transition activates for same-origin navigations where the navigation type is traverse, push, or replace, as long as the navigation does not include a cross-origin redirect.

Because the W3C CSS validator has not yet added support for this at-rule, the warning cannot be fixed by changing your code. The CSS itself is correct per the specification. Browser support is available in Chromium-based browsers (Chrome 126+, Edge 126+).

You can safely ignore this validator warning. If you want a completely clean validation output, move the `@view-transition` rule into a separate stylesheet so it does not interfere with validation of the rest of your CSS, or suppress the warning in your CI pipeline.