[csswg-drafts] [css-properties-values-api] Clarify whether `syntax: "<color> | "` is valid (#13610)

yisibl has just created a new issue for https://github.com/w3c/csswg-drafts:

== [css-properties-values-api] Clarify whether `syntax: "<color> | "` is valid ==
Safari can correctly parse `<color> |`, Safari can correctly parse `<color> |`, while Firefox and Chrome will consider this invalid syntax.

The specification does not appear to provide explicit examples illustrating how such cases should be handled.
https://drafts.css-houdini.org/css-properties-values-api/#the-syntax-descriptor

```html
data:text/html;charset=UTF-8,<!doctype html>
<style>
  @property --test1 {
    syntax: "<color> |";
    inherits: true;
    initial-value: red;
  }
  @property --test2 {
    syntax: "| <color>";
    inherits: true;
    initial-value: red;
  }
  div {
    display: inline-block; width: 100px; height: 100px;
  }
  .test1 {
    background-color: var(--test1, green);
  }
  .test2 {
    background-color: var(--test2, green);
  }
</style>
<p>You should see a green square below.</p>
<div class="test1"></div>
<div class="test2"></div>
```

<img width="714" height="402" alt="Image" src="https://github.com/user-attachments/assets/81771462-bcc4-4455-b8f0-9fd8baa77980" />

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/13610 using your GitHub account


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Received on Friday, 6 March 2026 12:34:08 UTC