Axes

The Axes section in the Style tab controls the appearance and behavior of the X axis and Y axis (or left and right Y axes in dual-axis charts). Most axis settings are available for all Vega-based chart types (bar, line, area, scatter, heatmap).

X axis

Setting	Description
Show axis	Toggle the X axis on or off
Title	Custom axis label — leave blank to hide the axis title
Grid lines	Toggle grid lines perpendicular to the X axis
Labels	Toggle axis tick labels
Label angle	Rotate axis labels (useful for long category names)
Label format	Number or date format applied to axis labels

Y axis (left)

Setting	Description
Show axis	Toggle the Y axis on or off
Title	Custom axis label
Grid lines	Toggle horizontal grid lines
Labels	Toggle axis tick labels
Label format	Number format applied to axis labels (e.g. $,.0f for currency)
Min / Max	Override the axis scale minimum and maximum values

Dual Y axis (right axis)

Add a second Y axis on the right side of the chart to plot a series on a different scale. This is useful for combining measures with different units or magnitudes — for example, showing order count on the left axis and average order value on the right.

To use the right axis:

1. In the Series configuration for a specific series, change the Y axis assignment from Left to Right.
2. The right axis settings appear in the Style tab — configure its title, labels, and scale independently from the left axis.

Reference lines

Add horizontal reference lines to mark a target, threshold, or benchmark value. Reference lines appear at a fixed Y value across the full width of the chart.

To add a reference line:

1. In the Y axis section of the Style tab, click Add reference line.
2. Set the Value — the Y position of the line.
3. Optionally set a Label that appears next to the line.
4. Configure Color and Style (solid, dashed, or dotted).

You can add multiple reference lines to the same axis. Each is configured independently.

Reference line labels

A reference line with no label renders as a bare rule — the reader has to already know what it means. Type text into Label to name it, for example Target 18k.

Once a label is set, two alignment controls appear next to it:

Control	Options	Description
Horizontal	Start / Middle / End	Where along the line the text sits
Vertical	Above / Below	Which side of the line the text sits on

New labels start at End and Above — the right end of the line, clear of the bars. The label takes the line's color, so it always reads as part of that line. Clearing the label removes the text and leaves the line itself untouched.

<Tip> A label on a line near the top or bottom edge of the plot flips to the other side of the line automatically, so the text stays inside the chart area. </Tip> <Note> Reference lines are only available on the left Y axis. For right-axis reference lines, use a [custom Vega-Lite spec](/docs/explore-analyze/charts/custom). </Note>