Track Every Step: Customer Journeys via Sankey Diagram

Customer journey mapping is the visual process of plotting a customer’s journey and analyzing their interactions with a brand.

This helps companies look at their business from the customer’s viewpoint. That, in turn, helps a business get insights into a customer’s pain points to be able to resolve them. This can be accomplished by

preparing charts, heatmaps, and other interactive visualizations, including the Sankey Diagram.

But running analyses with some numbers in a sheet for this kind of mapping does not inspire much thought. What is needed then is a well-constructed, easy-to-grasp visualization to understand how your customers move and interact with your brand.

According to the survey, the global data visualization market was valued at USD 4,874.4 million in 2020 and is projected to reach USD 6,570.7 million by the end of 2026, with a CAGR of 5.1% over the forecast period (2021-2026).

Also on the list is the Sankey Diagram, which offers a better understanding of the complex data required for customer path analytics. However, it has its own limitations, which we will discuss later in this post.

This data visualization tool provides a visual representation of the data flows within a system, including the flow of energy, materials, and even a customer’s journey in marketing.

What Is a Sankey Diagram?

As we had said in one of our earlier blog posts on the Sankey Diagram, this type of visualization is generally used to depict “a flow” from one set of values to the next.

They are so named after an Irishman, Capt. Matthew Sankey, who first used them in a publication on the energy efficiency of a steam engine in 1898.

You can use a Sankey map to visually demonstrate complex processes, focusing on a single aspect or resource. Such types of flow diagrams are useful when you’re making a decision about energy, time, or money.

Main Components of Sankey Diagram

The main components of the Sankey diagram consist of the following:

1. Nodes: Representing the events in each path, a "node" is an element linked by "Flows."

2. Flows: They link the nodes. Each flow is specified by the names of its target and source nodes in the "from" and "to" fields. The value in the width field defines the thickness of the flow.

3. Drop-offs: A drop-off is a flow without a target node and refers to the link that ends at the present node. It occurs when at least one path continues beyond a node.

Essentially, if you need to see where a certain amount is coming from, where it is going, and any in-between steps, you can use a Sankey diagram.

A user analysis diagram enables you to drill down to any level and can also help determine the optimal level of depth.

The first thing to notice about this flow diagram is that it uses both thick and thin lines. The thick lines are arrows. The thick lines indicate the amount of something entering or leaving a system.

The thin lines show how the quantity of the thing changes as it enters or leaves the system.

What is a Customer Journey Map?

Before delving deeper into the Sankey Diagram, let’s first understand what exactly a customer journey map is. As we said earlier in this post, it is a visual representation of the buyer’s movement across all touchpoints of your brand.

The latter is in the form of a website, social media channels, live chat, and even offline channels.

This customer journey mapping helps businesses get insights into common customer pain points, which, in turn, allows them to better optimize and personalize the customer experience.

An example: This kind of user journey can help you scientifically understand why a customer abandoned their cart on your e-commerce website and reduce such instances.

Was it because the payment gateway was too cumbersome to use? Or because the link to the gateway showed a 404 error? Another example could be a buyer shopping for a specific item on your website, then moving on to one of your social media channels to continue his/her shopping there.

Mapping Buyer Journeys with Sankey Diagrams

Sankey diagrams and Sankey charts were originally used for visualization and the analysis of energy flows, but they are a great tool to depict the flow of money, time, and resources, too.

Directional arrows between the nodes show the flows in a process, production system, or supply chain. What they help any business to do is to effectively communicate the data-based messaging to external or internal stakeholders like your customers or marketing teams, respectively.

In fact, a Sankey diagram or user journey diagram can be very useful in digital marketing analysis.

Can Sankey Diagrams Help in Churn Analysis?

Absolutely.

Customer retention often hides its most significant insights in small transitions: when, why, and how users disengage.

With a Sankey Diagram, you can map churn like this:

a) Stage 1: 1000 subscribers start Month 1

b) Stage 2: 850 renew for Month 2

c) Stage 3: 700 renewals for Month 3

d) Stage 4: 300 cancel after a price change

Now you can visualize:

a) Which feature drops correlate with churn

b) When churn spikes occur

c) How engagement patterns predict renewal likelihood

According to Forrester (2025), companies that use visual churn tracking reduce customer attrition by up to 21%, simply because they identify "silent exits" earlier.

Industry Applications of Sankey Diagrams

How to use Sankey Diagrams? Sankey diagrams can be used across many industries and sectors. They are frequently used in Finance for tracking cash outflows and inflows, expenditure, and finances.

In marketing, it is used by the data analytics team to cut out the guesswork and measure the effectiveness of the marketing campaigns in a more scientific way.

Sankey diagrams are also used in the Healthcare sector to stitch together a map of the patient’s journey – from the first consultation to the end of treatment.

Benefits of Using Sankey Diagrams

Simply collecting your customers’ behavior is not enough for any business. It needs to analyze the same for actionable insights. Sankey charts can do that by:

1. Supporting multiple viewing levels wherein one can drill down to granular insights or see specific details. Sankey charts offer multiple viewing levels.

Using different types of views, users can look at high-level details, view specifics, or generate interactive views.

If one of your team members likes to drill down, many tools let you share that functionality without having to spend extra time on the creator’s end.

Additionally, you can choose the depth that works best for your purposes.

2. Making your most prolific shoppers stand out. With a Sankey diagram, you can cross-check how many times a customer has viewed your product to find out if they are interested in it.

Interested customers will read the comments and reviews. Additionally, they may add it to their cart but not buy it.

3. Showing areas that can be improved upon. Why do some of your shoppers abandon their shopping carts? This is one such visualization that a Sankey Diagram can provide.

4. Showing areas with the largest opportunities. It means using this form of visualization to see which of your products or services are selling like hotcakes, and why.

Limitations of Sankey Diagrams

1. Sankey diagrams get cumbersome to draw when presenting complex data, say with three or more nodes. But this downside can be circumvented today with the availability of open-source tools.

2. When presenting a Sankey diagram, remember the one golden rule: the width of the lines and arrows represents the actual amounts or volumes of resources. Often, developers make a mistake here.

3. Overly complex data is a bit difficult to depict using a Sankey diagram.

4. Not best for comparison of values

How to Create a Sankey Diagram to Map a Customer's Journey

Our in-house data analyst, Mehar Singh Gambhir, explains how to actually develop and interpret a Sankey diagram to map a buyer’s journey:

In this particular example of visualizing a customer’s journey throughout his/her buying experience, we start by listing the various touchpoints (nodes) that a customer goes through before a purchase is made.

We have considered a basic e-commerce platform for this exercise and have depicted its traffic flow based on our experience of using and working with such platforms.

From landing on an online shopping website or opening an app to make a purchase, there are several nodes involved at various stages along which traffic is directed.

A company can track customers proceeding from one buying stage to another or find out how many of them have left abruptly.

A graphic visualization like the Sankey diagram or alluvial diagram, depicting the flow of traffic across several buying stages, is a handy tool for this purpose.

The nodes at each level can vary based on the company and depending on what data points the company wants to be covered.

A customer’s journey starts from landing on the company’s website or its app from different sources. The most common event cases can be listed as:

a) Direct logging into the website/app and browsing products

b) Landing via organic search (redirected from a search engine based on a product search without an ad/promotion)

c) Clicking on an advertisement link from an external website or social media

Based on our retail experience, these are the most common data points and links used to map a customer's journey in a Sankey diagram.

If the customer has the app, they browse there; if not, they continue on the website.

From here on, there are several possibilities of how this journey may end:

1. If they are really interested in the product, they view the product features in detail, along with its price, while some leave without any further activity

2. Some may read the reviews and ratings for the product, then add it to their cart, leave the page, or click on another product.

3. Others may only be visiting to review their previous purchase. These links help understand customer behavior online and how they react at different stages.

4. A few customers may proceed to checkout after adding items to their cart, while others may continue shopping and add more products to their cart.

5. Some customers may abandon their carts or clear their carts and exit. Even at the checkout, some customers decide against making a purchase. Or they may encounter an issue during payment, resulting in a lost sale.

This information can be used to find the weak links in the website/app and make respective improvements.

So, once the nodes and links were finalized, we started building this diagram. There are various tools available online through libraries in Python, R, and JavaScript. For our purposes, we used the Plotly library from Python to construct the Sankey diagram.

The first step was to count the nodes (n) and assign each node a number from 0 to n-1, followed by storing the labels for each node in numerical order in a list.

We designed this visualization with 15 nodes with 7 different levels and a total of 29 links between them. The distribution of traffic from one node to another is based on dummy data, but the actual traffic flow can be extracted from raw data through some processing.

The nodes involved are:

Level 0:

1. Landing From(0)

Level 1:

1. External Ad/Link(1)

2. Direct Search(2)

3. Organic Search (3)

Level 2:

1. Mobile App(4)

2. Official Website(5)

Level 3:

1. View product & details(6)

2. Read Reviews (7)

3. Click on another product (8)

Level 4:

1. Add to Cart (9)

Level 5:

1. Checkout(10)

2. Clear Cart(11)

Level 6:

1. Purchase(12)

2. Give Reviews/Ratings(13)

3. Exit(14)

After defining the nodes and their labels, separate lists of source and target nodes were created at each level for all the links.

Do not forget that the list of source and target nodes should be in the same order as the links. Another list for defining the weight of the links, following the same order, is called “value,” and that depends on the amount of traffic that moves from a source to a target node.

Then, while plotting the actual figure, we defined the colors and the width for the nodes as well as the links based on what information to depict in that combination.

What Are the Common Mistakes to Avoid?

Sankey Diagrams are powerful, but only when designed with clarity.

Avoid these pitfalls:

a) Too many nodes: Overcrowding confuses.

b) Inconsistent scaling: Always keep proportional line widths.

c) Lack of context: Add clear labels, legends, and tooltips to enhance clarity and understanding.

d) Overdecorating: Use color strategically; highlight insights, not aesthetics.

Remember, simplicity is sophistication. The best Sankeys show insight at a glance.

What Role Do Sankey Diagrams Play in Data Visualization Today?

In the age of AI-driven analytics, Sankey Diagrams bridge the gap between data science and storytelling.

They're used across various industries, including finance, manufacturing, healthcare, and marketing, to visualize cause-and-effect relationships.

For marketers, they unlock one core truth: how customers actually experience your brand.

According to McKinsey's "State of AI Marketing 2025," businesses that utilize advanced visualization techniques, such as Sankey flows, report a 37% higher campaign optimization efficiency and faster decision-making cycles.

It's not just about creating visually appealing content; it's about making data usable, understandable, and memorable.