n8n Expression Syntax

Expert guide for writing correct n8n expressions in workflows.

Detailed Guide

Read the detailed guide before executing this skill. It retains the complete procedure and reference material. Treat its safety, prerequisites, and validation requirements as mandatory. For focused work, load the relevant sections; for end-to-end work, read the guide completely.

When to Use

• You need to write or debug n8n expressions using {{ ... }} syntax.
• The task involves $json, $node, webhook payloads, or expression-related workflow errors.
• You want syntax-correct dynamic values inside n8n nodes and parameters.

When NOT to Use Expressions

❌ Code Nodes

Code nodes use direct JavaScript access, NOT expressions!

javascript
// ❌ WRONG in Code node
const email = '={{$json.email}}';
const name = '{{$json.body.name}}';

// ✅ CORRECT in Code node
const email = $json.email;
const name = $json.body.name;

// Or using Code node API
const email = $input.item.json.email;
const allItems = $input.all();

❌ Webhook Paths

javascript
// ❌ WRONG
path: "{{$json.user_id}}/webhook"

// ✅ CORRECT
path: "user-webhook"  // Static paths only

❌ Credential Fields

javascript
// ❌ WRONG
apiKey: "={{$env.API_KEY}}"

// ✅ CORRECT
Use n8n credential system, not expressions

Working Examples

For real workflow examples, see EXAMPLES.md

Example 1: Webhook to Slack

Webhook receives:

json
{
  "body": {
    "name": "John Doe",
    "email": "john@example.com",
    "message": "Hello!"
  }
}

In Slack node text field:

New form submission!

Name: {{$json.body.name}}
Email: {{$json.body.email}}
Message: {{$json.body.message}}

Example 2: HTTP Request to Email

HTTP Request returns:

json
{
  "data": {
    "items": [
      {"name": "Product 1", "price": 29.99}
    ]
  }
}

In Email node (reference HTTP Request):

Product: {{$node["HTTP Request"].json.data.items[0].name}}
Price: ${{$node["HTTP Request"].json.data.items[0].price}}

Example 3: Format Timestamp

javascript
// Current date
{{$now.toFormat('yyyy-MM-dd')}}
// Result: 2025-10-20

// Time
{{$now.toFormat('HH:mm:ss')}}
// Result: 14:30:45

// Full datetime
{{$now.toFormat('yyyy-MM-dd HH:mm')}}
// Result: 2025-10-20 14:30

Limitations

• Use this skill only when the task clearly matches the scope described above.
• Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
• Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.