# 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.borderWidth

The pixel width of the tooltip border. Defaults to 1, but with a `borderColor` to match the background in light mode, and a visible lighter border in dark mode.

In styled mode, the stroke width is set in the `.highcharts-tooltip-box` class.