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      <base href="https://bugs.webkit.org/" />
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    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - transition-duration doesn't work when using CSS variables"
   href="https://bugs.webkit.org/show_bug.cgi?id=169402">169402</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>transition-duration doesn't work when using CSS variables
          </td>
        </tr>

        <tr>
          <th>Classification</th>
          <td>Unclassified
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>WebKit
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>Safari 10
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>iPhone / iPad
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>iOS 10
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>Normal
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>P2
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>Animations
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>webkit-unassigned&#64;lists.webkit.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>rmmpaderes&#64;gmail.com
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>dino&#64;apple.com
          </td>
        </tr></table>
      <p>
        <div>
        <pre>As the title say, using a CSS variable for transition-duration doesn't work. However, if you use -webkit-transition-duration, it'll work fine.

Here's a sample CSS:

:root {
  --accent-color: green;
  --duration: 500ms;
}

.button {
  transition-duration: var(--duration);
  transition-property: color;

  // Adding -webkit-transition-duration works
  // -webkit-transition-duration: var(--duration);
}

.button:active {
  color: var(--accent-color);
}</pre>
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      <ul>
          <li>You are the assignee for the bug.</li>
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