Core Concepts

Understand the fundamental building blocks of n8n workflows. This guide explains how nodes, workflows, triggers, credentials, and expressions work together to create powerful automations.

Workflows

A workflow is a collection of connected nodes that execute in a specific order to accomplish a task. Workflows are represented as JSON objects in n8n.

Workflow Structure

Based on the source code (packages/workflow/src/interfaces.ts), a workflow consists of:

interface IWorkflowBase {
  id: string;                    // Unique workflow identifier
  name: string;                  // Workflow name
  active: boolean;               // Whether workflow is activated
  nodes: INode[];                // Array of nodes
  connections: IConnections;     // Node connections
  settings?: IWorkflowSettings;  // Workflow-specific settings
  staticData?: IDataObject;      // Persistent workflow data
  pinData?: IPinData;            // Pinned test data
}

Workflow Execution Modes

n8n supports several execution modes:

Manual

Triggered manually via the UI or API

Trigger

Activated by triggers (webhooks, schedules, polling)

Error

Executed when an error workflow is triggered

Webhook

Responds to incoming webhook requests

Example Workflow JSON

{
  "name": "Data Sync Workflow",
  "nodes": [
    {
      "id": "schedule-1",
      "name": "Schedule Trigger",
      "type": "n8n-nodes-base.scheduleTrigger",
      "typeVersion": 1,
      "position": [250, 300],
      "parameters": {
        "rule": {
          "interval": [{ "field": "hours", "hoursInterval": 1 }]
        }
      }
    },
    {
      "id": "http-1",
      "name": "Fetch Data",
      "type": "n8n-nodes-base.httpRequest",
      "typeVersion": 3,
      "position": [450, 300],
      "parameters": {
        "method": "GET",
        "url": "https://api.example.com/data"
      }
    }
  ],
  "connections": {
    "Schedule Trigger": {
      "main": [[{ "node": "Fetch Data", "type": "main", "index": 0 }]]
    }
  },
  "active": true
}

Nodes

A node is a single step in a workflow that performs a specific action. Nodes are the building blocks of automations.

Node Structure

From the source code, each node has:

interface INode {
  id: string;                    // Unique node instance ID
  name: string;                  // Node instance name
  type: string;                  // Node type (e.g., "n8n-nodes-base.httpRequest")
  typeVersion: number;           // Node version
  position: [number, number];    // Canvas position [x, y]
  parameters: INodeParameters;   // Node configuration
  credentials?: INodeCredentials; // Attached credentials
  disabled?: boolean;            // Whether node is disabled
  continueOnFail?: boolean;      // Continue workflow on error
}

Node Types

n8n has several categories of nodes:

1. Trigger Nodes

Trigger nodes start workflow execution:

Webhook Trigger
Schedule Trigger
Polling Trigger

Listens for incoming HTTP requests

// From packages/nodes-base/nodes/Webhook/
{
  "name": "Webhook",
  "type": "n8n-nodes-base.webhook",
  "parameters": {
    "path": "my-webhook",
    "httpMethod": "POST",
    "responseMode": "onReceived"
  }
}

Accessible at: https://your-domain.com/webhook/my-webhook

Executes on a schedule

{
  "name": "Schedule Trigger",
  "type": "n8n-nodes-base.scheduleTrigger",
  "parameters": {
    "rule": {
      "interval": [
        { "field": "minutes", "minutesInterval": 15 }
      ]
    }
  }
}

Periodically checks for new data

{
  "name": "Gmail Trigger",
  "type": "n8n-nodes-base.gmailTrigger",
  "parameters": {
    "event": "messageReceived",
    "filters": {
      "subject": "Invoice"
    }
  }
}

Polling triggers use getWorkflowStaticData('node') to persist state between polls.

2. Action Nodes

Perform operations with services:

{
  "name": "Send Email",
  "type": "n8n-nodes-base.emailSend",
  "parameters": {
    "fromEmail": "sender@example.com",
    "toEmail": "={{ $json.email }}",
    "subject": "Order Confirmation",
    "text": "Your order #={{ $json.orderId }} is confirmed"
  }
}

3. Core Nodes

Built-in utility nodes:

Code

Execute JavaScript or Python

HTTP Request

Make API calls to any service

Set

Transform and manipulate data

IF

Conditional routing

Switch

Multi-way branching

Merge

Combine data from multiple branches

Node Implementation

Nodes implement the INodeType interface (from packages/nodes-base/):

// Example from packages/nodes-base/nodes/HttpRequest/
export class HttpRequestV3 implements INodeType {
  description: INodeTypeDescription = {
    displayName: 'HTTP Request',
    name: 'httpRequest',
    icon: 'fa:at',
    group: ['output'],
    version: [3, 4, 4.1, 4.2, 4.3, 4.4],
    description: 'Makes an HTTP request',
    defaults: {
      name: 'HTTP Request',
      color: '#0004F5',
    },
    inputs: [NodeConnectionTypes.Main],
    outputs: [NodeConnectionTypes.Main],
    properties: [
      {
        displayName: 'Method',
        name: 'method',
        type: 'options',
        options: [
          { name: 'GET', value: 'GET' },
          { name: 'POST', value: 'POST' },
          { name: 'PUT', value: 'PUT' },
          { name: 'DELETE', value: 'DELETE' }
        ],
        default: 'GET'
      },
      {
        displayName: 'URL',
        name: 'url',
        type: 'string',
        default: '',
        required: true
      }
    ]
  };

  async execute(this: IExecuteFunctions): Promise<INodeExecutionData[][]> {
    const items = this.getInputData();
    const returnData: INodeExecutionData[] = [];
    
    for (let i = 0; i < items.length; i++) {
      const method = this.getNodeParameter('method', i) as string;
      const url = this.getNodeParameter('url', i) as string;
      
      const response = await this.helpers.httpRequest({
        method,
        url
      });
      
      returnData.push({ json: response });
    }
    
    return [returnData];
  }
}

Connections

Connections define how data flows between nodes.

Connection Structure

interface IConnection {
  node: string;              // Destination node name
  type: NodeConnectionType;  // Connection type (usually "main")
  index: number;             // Input/output index
}

interface IConnections {
  [sourceNodeName: string]: {
    [connectionType: string]: Array<IConnection[] | null>
  }
}

Connection Types

main: Regular data flow (default)
ai_agent: AI agent connections
ai_tool: AI tool connections
ai_memory: AI memory connections
ai_document: AI document connections

Example Connections

{
  "connections": {
    "Start": {
      "main": [
        [
          { "node": "HTTP Request", "type": "main", "index": 0 }
        ]
      ]
    },
    "HTTP Request": {
      "main": [
        [
          { "node": "IF", "type": "main", "index": 0 }
        ]
      ]
    },
    "IF": {
      "main": [
        [{ "node": "Success Handler", "type": "main", "index": 0 }],
        [{ "node": "Error Handler", "type": "main", "index": 0 }]
      ]
    }
  }
}

The connections object is indexed by source node. To find parent nodes, use the mapConnectionsByDestination() utility from n8n-workflow.

Data Flow

Node Execution Data

Data passed between nodes follows this structure:

interface INodeExecutionData {
  json: IDataObject;           // JSON data
  binary?: IBinaryKeyData;     // Binary files
  pairedItem?: IPairedItemData; // Source item tracking
}

interface IBinaryData {
  data: string;           // Base64 encoded or file ID
  mimeType: string;       // MIME type
  fileName?: string;      // Original filename
  fileExtension?: string; // File extension
  fileSize?: string;      // Human-readable size
  bytes?: number;         // Size in bytes
}

Processing Multiple Items

Nodes process items in batches:

// In a Code node
const items = $input.all();

// Process each item
const results = items.map((item, index) => {
  return {
    json: {
      originalId: item.json.id,
      processed: true,
      index: index
    },
    pairedItem: { item: index }  // Track source item
  };
});

return results;

Expressions

Expressions allow dynamic data access using the ={{ }} syntax.

Accessing Data

// Access current item data
{{ $json.fieldName }}
{{ $json["field-with-dashes"] }}
{{ $json.nested.field }}

// Access binary data
{{ $binary.fileName.data }}
{{ $binary.fileName.mimeType }}

// Access data from specific node
{{ $node["Node Name"].json.field }}

// Access specific item from node
{{ $node["Node Name"].item[0].json.field }}

// Access all items from node
{{ $node["Node Name"].itemMatching(0).field }}

// Workflow metadata
{{ $workflow.id }}
{{ $workflow.name }}
{{ $workflow.active }}

// Execution data
{{ $execution.id }}
{{ $execution.mode }}
{{ $execution.resumeUrl }}

// Environment
{{ $env.VARIABLE_NAME }}

Expression Functions

// String manipulation
{{ "hello".toUpperCase() }}
{{ $json.email.toLowerCase() }}
{{ $json.text.trim() }}

// Date/Time
{{ $now }}
{{ $today }}
{{ DateTime.now().toISO() }}
{{ DateTime.fromISO($json.date).plus({ days: 7 }).toISO() }}

// Math
{{ Math.round($json.price * 1.2) }}
{{ Math.max($json.value1, $json.value2) }}

// Arrays
{{ $json.items.length }}
{{ $json.items.map(i => i.name).join(", ") }}
{{ $json.items.filter(i => i.active) }}

// Conditionals
{{ $json.status === 'active' ? 'Active' : 'Inactive' }}

Expressions use JavaScript syntax and have access to built-in functions from Luxon (dates), lodash (utilities), and standard JavaScript.

Credentials

Credentials store authentication information securely.

Credential Structure

interface ICredentials {
  id?: string;
  name: string;      // User-defined credential name
  type: string;      // Credential type
  data?: string;     // Encrypted credential data
}

interface INodeCredentialsDetails {
  id?: string;
  name: string;
}

Using Credentials in Nodes

Nodes declare credential requirements:

{
  credentials: [
    {
      name: 'httpBasicAuth',
      required: true,
      displayOptions: {
        show: {
          authentication: ['basicAuth']
        }
      }
    },
    {
      name: 'httpHeaderAuth',
      required: true,
      displayOptions: {
        show: {
          authentication: ['headerAuth']
        }
      }
    }
  ]
}

Accessing Credentials in Code

// In a Code node or custom node
const credentials = await this.getCredentials('credentialType');

const apiKey = credentials.apiKey;
const apiUrl = credentials.apiUrl;

// Use in HTTP request
const response = await this.helpers.httpRequestWithAuthentication(
  'credentialType',
  {
    method: 'GET',
    url: apiUrl
  }
);

Common Credential Types

OAuth2

OAuth 2.0 authentication with automatic token refresh

API Key

Simple API key authentication

Basic Auth

Username and password authentication

Header Auth

Custom header authentication

Error Handling

Continue on Fail

Control error behavior at the node level:

{
  "name": "HTTP Request",
  "type": "n8n-nodes-base.httpRequest",
  "continueOnFail": true,
  "parameters": {
    "url": "https://api.example.com/data"
  }
}

When continueOnFail is true, errors are passed to the next node instead of stopping execution.

Error Workflows

Trigger a separate workflow on error:

Create an error workflow with a “Error Trigger” node
In your main workflow settings, select the error workflow
Errors will trigger the error workflow with context:

{
  "execution": {
    "id": "123",
    "mode": "trigger",
    "error": {
      "message": "API request failed",
      "node": "HTTP Request"
    }
  },
  "workflow": {
    "id": "456",
    "name": "Main Workflow"
  }
}

Retry on Fail

Configure automatic retries:

{
  "name": "HTTP Request",
  "retryOnFail": true,
  "maxTries": 3,
  "waitBetweenTries": 1000,
  "parameters": {
    "url": "https://api.example.com/data"
  }
}

Static Data

Persist data between workflow executions:

// In a Code node or trigger
const staticData = this.getWorkflowStaticData('node');

// Store last execution time
if (!staticData.lastRun) {
  staticData.lastRun = new Date().toISOString();
}

// Get items since last run
const newItems = items.filter(item => 
  new Date(item.json.createdAt) > new Date(staticData.lastRun)
);

// Update last run time
staticData.lastRun = new Date().toISOString();

return newItems;

Static data is stored in the database and persists across workflow executions. Don’t store large amounts of data.

Execution Context

Nodes have access to execution context through this:

interface IExecuteFunctions {
  // Get input data
  getInputData(): INodeExecutionData[];
  
  // Get parameter value
  getNodeParameter(name: string, index: number): any;
  
  // Get credentials
  getCredentials(type: string): Promise<ICredentialDataDecryptedObject>;
  
  // Helper functions
  helpers: {
    httpRequest(options: IHttpRequestOptions): Promise<any>;
    httpRequestWithAuthentication(type: string, options): Promise<any>;
  };
  
  // Workflow static data
  getWorkflowStaticData(type: 'node' | 'global'): IDataObject;
  
  // Context
  getExecutionId(): string;
  getWorkflow(): IWorkflow;
  getMode(): WorkflowExecuteMode;
}

Best Practices

Error Handling

Always configure error handling for production workflows using continueOnFail or error workflows

Expressions

Use expressions for dynamic data instead of hardcoding values

Credentials

Never hardcode credentials in workflows - always use credential system

Testing

Test workflows manually before activating with real data

Documentation

Use node notes to document complex logic

Modularity

Break complex workflows into smaller, reusable workflows

Advanced Topics

Workflow Versioning

Workflows support versioning:

{
  "versionId": "abc123",          // Current version ID
  "activeVersionId": "abc123"     // Active version ID
}

Pinned Data

Pin test data to nodes for consistent testing:

{
  "pinData": {
    "HTTP Request": [
      {
        "json": {
          "id": 1,
          "name": "Test Item"
        }
      }
    ]
  }
}

Sub-workflows

Call other workflows using the “Execute Workflow” node:

{
  "name": "Execute Workflow",
  "type": "n8n-nodes-base.executeWorkflow",
  "parameters": {
    "workflowId": "456",
    "source": "database"
  }
}

Learning Resources

Quick Start

Build your first workflow

Example Workflows

Browse 900+ templates

Node Reference

Documentation for all 400+ nodes

Community Forum

Ask questions and share workflows

This documentation is based on n8n version 2.9.0. Core concepts are stable, but specific node implementations may vary by version.

​Core Concepts

​Workflows

​Workflow Structure

​Workflow Execution Modes

Manual

Trigger

Error

Webhook

​Example Workflow JSON

​Nodes

​Node Structure

​Node Types

​1. Trigger Nodes

​2. Action Nodes

​3. Core Nodes

Code

HTTP Request

Set

IF

Switch

Merge

​Node Implementation

​Connections

​Connection Structure

​Connection Types

​Example Connections

​Data Flow

​Node Execution Data

​Processing Multiple Items

​Expressions

​Accessing Data

​Expression Functions

​Credentials

​Credential Structure

​Using Credentials in Nodes

​Accessing Credentials in Code

​Common Credential Types

OAuth2

API Key

Basic Auth

Header Auth

​Error Handling

​Continue on Fail

​Error Workflows

​Retry on Fail

​Static Data

​Execution Context

​Best Practices

Error Handling

Expressions

Credentials

Testing

Documentation

Modularity

​Advanced Topics

​Workflow Versioning

​Pinned Data

​Sub-workflows

​Learning Resources

Quick Start

Example Workflows

Node Reference

Community Forum

Core Concepts

Workflows

Workflow Structure

Workflow Execution Modes

Example Workflow JSON

Nodes

Node Structure

Node Types

1. Trigger Nodes

2. Action Nodes

3. Core Nodes

Node Implementation

Connections

Connection Structure

Connection Types

Example Connections

Data Flow

Node Execution Data

Processing Multiple Items

Expressions

Accessing Data

Expression Functions

Credentials

Credential Structure

Using Credentials in Nodes

Accessing Credentials in Code

Common Credential Types

Error Handling

Continue on Fail

Error Workflows

Retry on Fail

Static Data

Execution Context

Best Practices

Advanced Topics

Workflow Versioning

Pinned Data

Sub-workflows

Learning Resources