This entry is part of the Chart Index, the reference library for the Chart Design Field Guide.

The stacked area chart is a line chart's contribution to part-to-whole over time. Several series are stacked on top of each other, the height at any point being the sum of all series at that point. The streamgraph is a stacked area variant where the baseline is not zero but is centred — the whole composition flows symmetrically around a horizontal axis, producing the river-like shape that gave the form its name.

Both forms answer the same question: how does the composition of a total evolve over time? The stacked area is more honest about absolute totals; the streamgraph is more elegant about shifting composition, at the cost of precise reading.

What it is

A stacked area chart maps time to the x-axis and a quantitative variable to the y-axis. Several series are summed into stacks: the bottom series sits on zero, the next series sits on the first, and so on. Each series is filled with a distinct colour. A streamgraph applies the same stacking but centres the baseline — the total flows symmetrically above and below a moving central axis. Lee Byron and Martin Wattenberg formalised streamgraphs in 2008 as part of Listening History visualisations.

Music streaming by genre — 24 months2025-2026 · 8 genres · hours streamed · streamgraph baseline

Eight music genres across two years. The streamgraph's central baseline makes shifts in composition visually dominant: one genre's bulge as it grows, another's narrowing as it declines. Reading exact totals at a single time point is harder than with a stacked area — but the flow of the music landscape over time is unmissable.

When to use it

Streamgraphs and stacked areas are the right choice when:

  • The data is multi-series time-series with a part-to-whole structure.
  • The reader's question is "how is the composition changing?" more than precise totals.
  • You have 4–10 series. Fewer and a line chart suffices; more and the form becomes unreadable.
  • The chart is editorial or visualisation-led — streamgraphs especially.
  • You have substantial change in composition over the time range — flat compositions make the form decorative.

When not to use it

  • Precise comparison. Both forms make it hard to read the value of a non-bottom series at a specific time. For precision, use small-multiple line charts.
  • Many series (10+). Stacks of thin bands become unreadable. Switch to small multiples or aggregate categories.
  • Operational dashboards. The forms are exploratory and editorial. For dashboards, use simpler stacked bars or line charts.
  • Negative values. Stacking assumes non-negative contributions. Mixed signs break the form.

Design principles

Order series by stability and value

Place the most-stable series at the baseline (bottom for stacked area, central for streamgraph). The series with the most fluctuation should sit near the visual edges, where the wiggling is naturally more tolerable to the eye.

Stacked series share semantics. Use a single hue family with varying lightness, or a desaturated categorical palette. Rainbow palettes produce bands of competing colour.

Choose the baseline deliberately

Stacked area: baseline at zero, conventional. Streamgraph: baseline centred (mean = 0), elegant for compositional flow. Or Wiggle baseline (Byron and Wattenberg) — algorithmically smoothed for minimum slope. The choice changes how the chart reads.

Stacked area vs. streamgraph — same data, different baselines
STACKED AREA — ZERO BASELINESTREAMGRAPH — CENTRED
The stacked area anchors at zero and shows absolute totals; the streamgraph centres the baseline and shows compositional flow.

Label series directly

Each filled region should be labelled inside its own band or with a leader line. Legends force the reader's eye to shuttle between the chart and a colour key.

Show the total as a thin top line

For stacked area charts, optionally trace the top of the stack with a thin line in a different colour — this is the total, the chart's most important single value. The thin line is read as a line chart and the bands below give the composition.

Use streamgraph only when composition is the message

Streamgraphs sacrifice precise reading of totals for elegance and flow. Only use them when the chart's story is how the mix has changed over time and your audience is comfortable with the editorial form.

Annotate notable transitions

If a series surges or collapses, annotate it. Genre X surged after the 2025 awards. The streamgraph shows the shape; the annotation explains it.

Anatomy

The Composition of a Streamgraph
PopHip-HopElectronicCountryJazzJan 25Jul 25Jan 26Jul 26STREAMGRAPH — CENTRED BASELINECENTRE BASELINE
An anatomical guide

A streamgraph's anatomy is a set of filled bands flowing above and below a central baseline, with direct labels and a time axis. The form is decorative and informative simultaneously; design choices balance the two.

  • Stacked area — the same form anchored at zero.
  • 100% stacked area — normalised to show composition only.
  • Multi-line chart — for precise reading of individual series over time.
  • Ridge plot — for stacked distribution shapes rather than time-series.
  • Stream + line overlay — streamgraph with a single line traced through one series; the editorial hybrid.

Reading list

  • Byron, L. & Wattenberg, M. (2008). Stacked Graphs — Geometry & Aesthetics. The original streamgraph paper.
  • Havre, S., Hetzler, B. & Nowell, L. (2000). ThemeRiver: Visualizing Theme Changes Over Time. The precursor to streamgraphs.
  • The New York Times graphics desk (2008-present). The form's editorial home in journalism.