A scale is a transformation that enlarges or shrinks a data domain so that it fits a specific range. Chart.js scales data automatically, adjusting domain data values so they fit within the space reserved for the chart. A scale is represented by an axis, which is a directed line that represents the extent of the domain. The discrete values that are placed on an axis line are called ticks. A coordinate system with perpendicular or radial axes and discrete ticks forms a grid. Scales, axes, ticks, and grids exist in all charts, even if you don’t see them. They control how the data points will be displayed in the chart.

Cartesian charts have two scales, each represented by perpendicular axes, x and y, and radial charts have one scale, represented by the radius and angle. Radial scales are always linear, but Cartesian scales can be linear, logarithmic, categorical, or temporal. Chart.js also allows you to create your own scales.

In most charts, the axes, grid lines, and tick labels are visible by default, but you may wish to remove unnecessary lines, lighten colors, dash lines, and hide unused legends to maximize the data-ink ratio of your chart. Font sizes and colors can be configured for all labels, and you can conditionally hide data using callbacks.