# 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.header.style

CSS styles for the tooltip header. The default is `{ fontSize: '1em' }`, ensuring that the header text is the same size as the axis labels.