When should I use a alluvial chart?

Showing how categorical membership changes across sequential stages ● Tracking voter migration between parties across elections ● Visualizing how students move through academic programs over time

When should I avoid a alluvial chart?

When you have only two stages (a Sankey or slope chart is clearer) ● When there are many small categories that create visual noise ● When precise quantitative comparisons are needed

What are common mistakes with alluvial charts?

Using too many categories, making the ribbon structure unreadable ● Not ordering categories consistently to minimize crossings ● Forgetting to label the stages/columns

What data does a alluvial chart need?

Minimum 8 rows, 3 columns (string, string, number). Requires source category, target category, and a flow weight for each stage transition.

Ranking

Alluvial Chart

Visualizes categorical flows across multiple stages using curved bands whose width encodes quantity, revealing how groups merge and split.

Student Major Migration

How a freshman cohort changes majors across four years

View data (17 rows)

Chart data table: Student Major Migration
Year 1	Year 2	Year 3	Year 4	Count
Engineering	Engineering	Engineering	Engineering	320
Engineering	Engineering	Business	Business	40
Engineering	CS	CS	CS	60
Engineering	Undeclared	Business	Business	30
CS	CS	CS	CS	260
CS	CS	CS	Data Science	50
CS	Engineering	Engineering	Engineering	25
Business	Business	Business	Business	200
Business	Business	Economics	Economics	45
Business	Economics	Economics	Economics	30
Biology	Biology	Biology	Biology	150
Biology	Biology	Pre-Med	Pre-Med	60
Biology	Psychology	Psychology	Psychology	25
Undeclared	Business	Business	Business	80
Undeclared	CS	CS	CS	55
Undeclared	Psychology	Psychology	Psychology	40
Undeclared	Biology	Biology	Biology	25

Make an alluvial chart with your data

Use an alluvial chart when…

Showing how categorical membership changes across sequential stages
Tracking voter migration between parties across elections
Visualizing how students move through academic programs over time

Avoid when…

When you have only two stages (a Sankey or slope chart is clearer)
When there are many small categories that create visual noise
When precise quantitative comparisons are needed

Data it needs

Property	Value
Min Rows	8
Min Columns	3
Column Types	stringstringnumber
Notes	Requires source category, target category, and a flow weight for each stage transition.

Visual anatomy

Marks

ribbonrectangle

Channels

width (quantity)color (category)vertical position (stack order)

Axes

horizontal: stages/columns

Guiding principles

Consider instead

Sankey Diagram

When flows represent energy, money, or resource transfers

Bump Chart

When you care about rank order rather than volume

Common mistakes

Using too many categories, making the ribbon structure unreadable
Not ordering categories consistently to minimize crossings
Forgetting to label the stages/columns

History

Alluvial diagrams were introduced by Martin Rosvall and Carl Bergstrom in 2010 to visualize changes in network community structure over time. The name comes from the resemblance to alluvial fans in geology where rivers split and merge.

Accessibility notes

Screen readers should announce each flow band with its source, target, and volume. Provide a structured table of transitions. Use distinct colors with sufficient contrast for adjacent ribbons.

Got data? Let's see what works.

Drop your CSV. You'll get an Alluvial Chart plus four alternatives - ranked by which one actually fits your data best.

Try it free