A stacked area chart visualizes the evolution of multiple categories over time by stacking the values of each category on top of each other. It’s particularly useful to show how the total and its sub-components change over a continuous variable like time.
An example use case is tracking website visits from different traffic sources (organic, direct, referral, social) over the course of a year. The area for each source is stacked, allowing for a clear view of how much each contributes to the overall trend.
However, stacked area charts can become hard to read when many categories are involved. They are best used when the number of categories is limited and the total is as relevant as its parts.