Legends

Note: This guidance is a work in progress. To see our roadmap, make feature requests, or contribute, please go to carbon-charts GitHub repository.

When possible, avoid using a legend and label data representations directly. Legends rely on visual association, which can make a chart more difficult to understand.

Your chart doesn’t need a legend if it only presents one data category. Only use a legend if you can’t safely assume there will be enough space to apply labels directly.

Use clear language and avoid acronyms in legends. This also applies to titles and axis labels.

Remove legends to simplify the chart when only one data category is needed or only one color is used.

In-chart labels are ideal for charts with predictable data and ample empty space.

Color and texture

Chart legends use color as the default distinguishing property for data sets and values. Texture can be used instead of, or in addition to, color to make your chart accessible for users with visual impairment.

Texture can improve accessibility. See the accessibility page for all approved textures.

The legends are positioned at the bottom of a chart by default. Depending on the page’s layout and context, you may choose to position the legends at the top, under the chart title, left or right of a chart with respect to the graph frame.

Position the legend at the bottom or top of a chart in situations where space is scarce, such as a dashboard.

Position the legend to the left of the chart when better type alignment is needed. Be sure the surrounding elements of the chart are not too closely clustered.

Position the legend to the right of the chart when space is plentiful, or when you would like to provide the maximum context. In mobile, the legend could revert to a stack.

In geospatial charts, legends can be overlaid on top of a graph frame as long as the legend has a background opacity of 80% of the chart’s background color. Since geospatial charts can vary drastically in appearance, the legend can be placed on either side of the chart, top- or bottom-aligned, whatever best accommodates the content.

To demonstrate the legend’s background opacity, we chose to place the legend at the top left in the chart below. See the Master data visualization design file for more detail about geospatial legends.

Hovering over the legend of one category lowers the opacity of all other categories in the chart to 30 percent.

Clicking on the legend of one category isolates the information, hiding all other categories. The legend gets a checkmark on click, switching to a selected state.

When all categories are selected, checkmarks in legends disappear and the legend resets to its default state.

Please note that hiding legends is discouraged in data visualizations unless only one category of data is displayed. This design is for mobile displays where offering legends at a glance is less essential. In general, hiding legends reduces the clarity of the visualization and is inaccessible.

On mobile, hide legends and reveal on tap

When legends are hidden, a “View legends” button is added so users can surface the legend on tap.

When clicking on “View legends”, a modal with a list of legends appears with options to toggle each data category on and off.

Up to two lines of legends are displayed by default. Clicking on View more expands the legend area to show all legends. A legend should not be taller than 30 percent of the chart’s height.

Legends default to a maximum of two lines. "View more" may expand to 30 percent of the chart.

When legends exceed 30 percent of the chart, overflow the content and scroll vertically.

Overflowing legends have vertical scrolling applied.

Usage

Color and texture

Position

Bottom (default) and top

Left

Right

Overlay (geospatial only)

Interactions

Hover to highlight

Click to isolate

Hidden legends

Legend overflow