<!DOCTYPE html>
<html>
    <head>
        <title>auto-height multicol with break</title>
        <script>
            if (window.internals)
                internals.settings.setRegionBasedColumnsEnabled(true);
        </script>
        <style>
            .mc > div { padding:0 0.5em; }
        </style>
    </head>
    <body style="min-width:40em;">
        <div class="mc" style="-webkit-columns:3; -webkit-column-gap:1em; columns:3; column-gap:1em; orphans:1; widows:1; width:32em; background:olive;">
            <div>
                first column<br>
                first column<br>
                first column<br>
                first column<br>
                second column<br>
                second column<br>
                second column<br>
            </div>
            <div style="-webkit-column-break-before:always; break-before:column;">
                third column<br>
            </div>
        </div>
    </body>
</html>