# JS API Reference

# Welcome to the Highcharts JS 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.pareto.tooltip.xDateFormat

The format for the date in the tooltip header if the X axis is a datetime axis. The default is a best guess based on the smallest distance between points in the chart.