Heatmap series
A heatmap displays a grid of cells, using color to encode a value at each X/Y position.
When to use
Use it to find patterns in a matrix, such as activity by weekday and time of day. Use a consistent numeric color scale across cells; use labels or tooltips when exact values matter.
Example
Data
Set type: 'heatmap'. Each cell contains x, y, and value. With category axes, pass zero-based indices into xAxis.categories and yAxis[].categories. With continuous axes, pass coordinates.
Series options
Null values leave gaps by default; set nullMode: 'zero' to treat them as zero. Use borderWidth and borderColor to separate cells.
Colors
Assign each point’s color from its numeric value, as in the example. The chart does not derive cell colors from value or the legend scale; cells without a point color use the series color. Use the same color mapping for the cells and legend.
Legend
Use legend.type: 'continuous' with legend.colorScale.colors, domain, and stops to explain the cell colors. For a two-color scale spanning the full domain, set stops: [0, 1]. This configures only the legend, so keep it in sync with the mapping that assigns point colors. See Continuous legend.