I'm trying to define a larger fontSize for tooltip, but it only updates value tooltip, timestamp one keeps on default value. What option I should change? I cound't find anywhere on api.
Here is the demo link.
The tooltip header has set inline font size by default:
'<span style=\"font-size: 10px\">{point.key}</span><br/>'
You can overwrite this value or remove it, then the header will inherit from tooltip style settings.
tooltip: {
style: {
fontSize: '18px'
},
headerFormat: '<span>{point.key}</span><br/>'
}
Demo: https://jsfiddle.net/BlackLabel/8np2m5ua/
API: https://api.highcharts.com/highstock/tooltip.headerFormat