Transforming Data with the Set Node

Hello! Let's dive into the next step of mastering n8n.

In our last lesson, you learned how to use the Expression Editor to dynamically access data from previous nodes. This is a crucial skill for making workflows responsive. We saw how expressions, like {{ $json.order_id }}, can pull live data into a node's parameters.

Today, we'll build directly on that knowledge. Accessing data is one thing, but often you'll need to clean, reshape, or enrich it before passing it on. For this, we'll use one of the most fundamental and powerful nodes in n8n: the Set node. This lesson will show you how to apply basic data transformations, which is essential for almost any workflow that handles data from different sources.

Given your background as a software developer, you can think of the Set node as a tool for mapping one data structure to another—like creating a Data Transfer Object (DTO) from a raw API response to fit the exact schema required by the next service in your pipeline.

1. The "Swiss Army Knife" for Data: The Set Node

The Set node (which you'll find in the node panel as "Edit Fields") is your primary tool for manipulating the data of each item that flows through it. Its purpose is simple but powerful: it allows you to add, modify, rename, and remove fields within a JSON item.

This is critical when:

• An API gives you 50 fields but you only need three.
• A field is named cust_name, but your database requires customerName.
• A price comes in as a string ("99.99") but you need it as a number for calculations.
• You need to create a new field by combining existing ones (e.g., firstName and lastName).

Now, let's see how to perform these transformations in practice.

2. Core Transformations with the Set Node

The Set node offers a straightforward interface for common data manipulation tasks. We'll explore the most important ones. The following video provides excellent hands-on examples for each.

Adding and Modifying Fields

Your first step is often to add new information or change what's already there. This could be adding a static status field or converting a data type.

As you saw, you can:

• Add a new field: Click "Add Field", give it a name, select its data type, and provide a value.
• Modify an existing field: Enter the name of the field you want to change, and provide a new value or type. The new value will overwrite the old one.

Combining Fields with Expressions

This is where your knowledge from the last lesson comes into play. You can use expressions to create new fields based on the values of existing ones. A classic example is creating a full_name field from first_name and last_name.

The expression {{ $json.first_name + ' ' + $json.last_name }} is a perfect example of using the skills you already have inside the Set node to generate new, more useful data.

3. Shaping the Output: Keeping Only What You Need

Often, the goal of a Set node is to create a clean, well-defined data structure for the next node. You don't want to pass along all the messy, irrelevant fields from the input.

This is where you control the final output of the node.

To achieve this clean output, you need to manage which fields are passed through.

This is a vital concept. While the video shows the "Include Other Input Fields" option, in modern n8n versions you may see a simpler toggle called Keep Only Set. If you enable this, only the fields you explicitly define in the Set node will be in the output. All other input fields are discarded. This is the most direct way to create a clean data structure.

4. On-the-Fly Transformations with JavaScript

Since expressions are JavaScript, you can use built-in methods for quick data formatting.

This technique is incredibly efficient for simple data hygiene tasks like standardizing casing or breaking a string into an array.

{
  "product_id": "sku-f5b3",
  "customer": {
    "first": "jane",
    "last": "doe"
  },
  "purchase_price": "149.99",
  "source": "api-v1"
}

{
  "customerName": "Jane Doe",
  "price": 149.99,
  "productID": "SKU-F5B3"
}

Conclusion

You've now added a powerful and versatile tool to your n8n arsenal. The Set node is the workhorse of data transformation, enabling you to prepare data for any destination.

Key Takeaways:

• Core Function: The Set node is used to add, modify, rename, and remove fields in your workflow's data items.
• Expressions are Key: The Set node works hand-in-hand with expressions to create dynamic values and combine data.
• Data Shaping: Options like "Keep Only Set" are crucial for cleaning up messy data and creating a precise output structure.
• Inline Logic: You can use standard JavaScript functions and methods within expressions for efficient, on-the-fly transformations.

We've learned how to access data with expressions and how to transform it with the Set node. But what if we need to perform different actions based on the value of that data? For example, "if the order total is over $100, send an email to the manager; otherwise, just log it."

In our next lesson, we will explore conditional logic by learning how to use the If node to create different branches in a workflow, allowing you to build much more intelligent and flexible automations.