---
title: Debug Node
---

Workflow or Chatflow application is made up of multiple interconnected nodes. To make sure everything works as intended, it’s crucial to test how each node handles input and produces output — before going live.

With the Step Run feature, you can catch potential issues early by verifying your application’s behavior step by step — helping you avoid errors before publishing.

There are two types of node debugging: single-step run and step-by-step execution.

## Single-Step Run

### Overview

Single-step run allows you to test a specific node in isolation without executing the entire workflow. It is helpful for verifying new nodes, troubleshooting individual node errors, or testing responses to various inputs.

### How to Use

1. Select the node you want to debug in the workflow editor  
2. Provide test input variables in the node’s settings panel  
3. Click **Run** to execute the node  
4. Review the output and check if the results are as expected

### Example

Suppose you've added an HTTP node. To verify whether it correctly fetches and handles API responses, you can use single-step run to simulate actual conditions and confirm it passes data correctly to downstream nodes.

![](https://assets-docs.dify.ai/2025/04/376c9de6f92cb7a5f97a6661c5e0e9eb.png)

After debugging, you can click "Last run" to check execution status, view inputs/outputs, and inspect metadata. If an error occurs, the message will help you locate and fix the problem to avoid full workflow failure.

<Warning>
    Answer and End nodes do not support single-step run.
</Warning>

## Step-by-Step Execution

### Overview

Workflow execution relies on proper data flow between nodes. In complex workflows, this process can easily fail due to:

- Data format mismatches (e.g., text passed to a number input)
- Misconfigured variables
- JSON parsing failures
- Incorrect variable path references

Step-by-step execution helps developers troubleshoot errors in multi-node workflows. 

During this process, node output variables are cached in the [Variable Inspector](/en/guides/workflow/debug-and-preview/variable-inspect). You can edit upstream variables directly to test how downstream nodes respond to different data values.

This method is particularly useful when your workflow contains nodes that depend on each other’s outputs. Rather than rerunning the entire chain, you can simulate different scenarios quickly by editing cached variables.

![](https://assets-docs.dify.ai/2025/06/f8656d8deeeaefeab0a8d9169f0ed2d3.png)

After running a node, its output is saved to the Variable Inspector. You can use this tool to:

1. **View actual data**: Check if the output meets expectations  
2. **Edit test data**: Modify variable values to test downstream behavior  
3. **Validate data flow**: Ensure values are correctly passed between nodes

### How to Use

1. Run a single node in the workflow
2. Open the Variable Inspector at the bottom  
3. Locate the node and check which variables it references  
4. Modify those variable values and rerun the node  
5. Compare results and evaluate impact

### Example

Suppose your workflow has the following steps: Data Fetch (Node A) → Data Processing (Node B) → Result Display (Node C).

Node B depends entirely on the output of Node A, and different inputs will change its behavior.

After running Node A, its output will be cached in the Variable Inspector. You can modify that data directly and rerun Node B without needing to re-execute Node A.

This approach lets you observe localized behavior and make timely adjustments to node settings, data flow, and logic, improving overall workflow reliability and accuracy.

## View Node Execution History

Every time a node is executed, a record is generated. Click “Last run” on the node details panel to view it.

![](https://assets-docs.dify.ai/2025/04/5ee92e6406979f5101d21865f95a86e5.png)

To view the full workflow’s execution history, see [Run History](/en/guides/workflow/debug-and-preview/history-and-logs).

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