# 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.gantt.tooltip.headerFormat

The HTML of the tooltip header line. The context is the Point class. Variables are enclosed in curly brackets. Examples of common variables to include are `x`, `y`, `series.name` and `series.color` and other properties on the same form. The `point.key` variable contains the category name, x value or datetime string depending on the type of axis. For datetime axes, the `point.key` date format can be set using `tooltip.xDateFormat`. In v12+, locale-aware date names follow the browser's casing and can be lower-case, so use the `ucfirst` helper (for example `{ucfirst point.key}`) if you want a capitalized header.