# 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.

# plotOptions.series.tooltip.clusterFormat

The HTML of the cluster point's in the tooltip. Works only with marker-clusters module and analogously to pointFormat.

The cluster tooltip can be also formatted using `tooltip.formatter` callback function and `point.isCluster` flag.