Working with n8n Variables: A Comprehensive Guide

Unlock the full potential of your workflows by understanding the n8n variable system. This guide demystifies the two main types of variables and shows you how to use them effectively for both static configuration and dynamic data handling.
n8n Variable Guide: Custom & Static Data Explained

Working with n8n Variables: A Comprehensive Guide

To properly use an n8n variable, you must first understand that n8n offers two distinct methods for storing and accessing data that function like variables: instance-level Custom Variables and execution-level Workflow Static Data. Custom Variables (`$vars`) are read-only, instance-wide values ideal for storing static configurations like API keys or environment-specific URLs. Conversely, Workflow Static Data (`getWorkflowStaticData()`) provides a read/write storage space that persists only for the duration of a single workflow execution, making it perfect for dynamic tasks like tracking items in a loop or passing data between complex branches.

Let’s talk about a topic that trips up even seasoned n8n users: variables. You’d think it would be simple, right? Just declare a variable and use it. But in the world of n8n, the answer is a classic “it depends.” The confusion often stems from not realizing there are different tools for different jobs. Getting this right is the difference between a brittle, confusing workflow and a robust, elegant automation. As an n8n professional, I’ve seen this firsthand countless times—it’s a foundational concept that unlocks truly powerful workflow design.

The Two Main “Variable” Types in n8n: What’s the Difference?

At its core, the choice comes down to one question: Is your data static or dynamic? Is it something you set once and use everywhere, or is it something that needs to change *during* a workflow run? Let’s break down the two main approaches.

Instance-Level Custom Variables (The `$vars` Object)

Think of Custom Variables as constants written on a giant whiteboard in your office. Everyone in your n8n instance can see them and use them, but no one can change them with an eraser (at least, not from within a workflow). This feature, primarily available on Self-hosted Enterprise and Pro/Enterprise Cloud plans, is a lifesaver for managing configurations.

Here’s the lowdown:

  • Scope: Global. Available to every workflow in your n8n instance.
  • Mutability: Read-only within a workflow. You must use the n8n UI to set or change their values.
  • Access: Simple and clean, using the `$vars` object. For example: {{ $vars.my_api_key }}.

The killer use case? Managing environments. Let’s say you have a development, staging, and production setup. Instead of hardcoding the API base URL in every HTTP Request node, you can create a variable called api_base_url. In your dev instance, you set its value to https://dev-api.mycompany.com. When you move the workflow to production, you just update the variable’s value in the production instance’s UI to https://api.mycompany.com. No workflow edits required. It’s clean, efficient, and far less error-prone.

Execution-Level Static Data (`getWorkflowStaticData`)

Now, here’s where it gets interesting. What if you need a variable that changes *during* a workflow? This is the problem that pops up constantly in community forums, especially with loops. For this, we turn to Workflow Static Data.

The name is a bit of a misnomer; it’s anything but static. I prefer to think of it as an “execution scratchpad.” It’s a temporary data store that is born when your workflow starts and dies when it finishes. Each execution gets its own, clean scratchpad.

Key characteristics:

  • Scope: Execution-level. The data is only available within the single run of the workflow where it was created.
  • Mutability: Read/write. You can create, update, and delete values from it using a Code node.
  • Access: Accessed via the built-in getWorkflowStaticData() function within a Code node.

Real-World Example: Taming a Loop with Static Data

Let’s tackle a common scenario. You need to process a list of 100 customer records from a database and send each one to an external API. You want to keep a running count of how many succeeded and how many failed.

If you used a Set node inside the loop to increment a counter, you’d quickly find that its value isn’t easily accessible across different branches or after the loop finishes cleanly. It gets messy. Here’s the elegant solution using static data:

  1. Initialization (Before the Loop): Add a Code node to set up your scratchpad.

const staticData = getWorkflowStaticData();

// Initialize counters
staticData.successCount = 0;
staticData.failureCount = 0;

return []; // Pass along the original data to the loop
  1. Inside the Loop (After the API call): Use an IF node to check if the API call was successful.
  2. Increment Success: On the “true” path of the IF node, add a Code node to increment the success counter.

const staticData = getWorkflowStaticData();
staticData.successCount++;
return item;
  1. Increment Failure: On the “false” path, add a Code node to increment the failure counter.

const staticData = getWorkflowStaticData();
staticData.failureCount++;
return item;
  1. Final Report (After the Loop): Add a final Code node to retrieve the totals from your scratchpad and format a report.

const staticData = getWorkflowStaticData();

const report = {
  message: "Processing complete!",
  successful_records: staticData.successCount,
  failed_records: staticData.failureCount
};

return report;

With this method, you have a reliable state that persists across all iterations and branches of your single workflow execution. It’s a game-changer.

Choosing Your n8n Variable Strategy

So, how do you decide what to use? Let this simple table be your guide.

Goal Recommended Method Best For… Watch Out For…
Store a static value for all workflows (e.g., an API key or Base URL). Custom Variables ($vars) Managing configurations, environment settings, and preventing hardcoded secrets. This is an Enterprise/Pro feature. The value is read-only in workflows.
Track a changing value within a single workflow run (e.g., a loop counter). Workflow Static Data Loops, complex branching logic, and maintaining state during one execution. Data is erased after the execution ends. It’s not for persistence between runs.
Share a value between different workflow runs (e.g., last run timestamp). External Storage (Database/Sheet) Creating stateful workflows that need to remember past events. Adds complexity and an external dependency (e.g., Redis, Postgres, Google Sheets).

Let’s be honest, sometimes you need something that persists between runs but doesn’t require a full database setup. For self-hosted users, the community has developed nodes like @telepilotco/n8n-nodes-kv-storage that provide a simple in-memory key-value store. It’s a fantastic middle ground, but be aware that since it’s in-memory, the data is typically lost if you restart your n8n instance.

Mastering these variable concepts is fundamental to leveling up your n8n skills. By understanding the distinction between instance-wide constants and execution-scoped data, you can build automations that are not only more powerful but also significantly easier to maintain and debug. Happy automating!

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