# Welcome to the Highcharts Gantt JS (gantt) Options Reference

These pages outline the chart configuration options, and the methods and properties of Highcharts objects.

Feel free to search this API through the search bar or the navigation tree in the sidebar.

# tooltip.borderColor

The color of the tooltip border. When `undefined` or `null`, the border takes the color of the corresponding series or point.

By default, in light mode the border color matches the background color because the shadow makes the tooltip stand out. In dark mode, a visible line is used because the default shadow is too dark to be visible on a dark background.