n8n Expression Syntax

Expert guide for writing correct n8n expressions in workflows.

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Expression Format

All dynamic content in n8n uses double curly braces:

{{expression}}

Examples:

✅ {{$json.email}}
✅ {{$json.body.name}}
✅ {{$node["HTTP Request"].json.data}}
❌ $json.email  (no braces - treated as literal text)
❌ {$json.email}  (single braces - invalid)

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Core Variables

$json - Current Node Output

Access data from the current node:

{{$json.fieldName}}
{{$json['field with spaces']}}
{{$json.nested.property}}
{{$json.items[0].name}}

$node - Reference Other Nodes

Access data from any previous node:

{{$node["Node Name"].json.fieldName}}
{{$node["HTTP Request"].json.data}}
{{$node["Webhook"].json.body.email}}

Important:

• Node names must be in quotes
• Node names are case-sensitive
• Must match exact node name from workflow

$now - Current Timestamp

Access current date/time:

{{$now}}
{{$now.toFormat('yyyy-MM-dd')}}
{{$now.toFormat('HH:mm:ss')}}
{{$now.plus({days: 7})}}

$env - Environment Variables

Access environment variables:

{{$env.API_KEY}}
{{$env.DATABASE_URL}}

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🚨 CRITICAL: Webhook Data Structure

Most Common Mistake: Webhook data is NOT at the root!

Webhook Node Output Structure

{
  "headers": {...},
  "params": {...},
  "query": {...},
  "body": {           // ⚠️ USER DATA IS HERE!
    "name": "John",
    "email": "[email protected]",
    "message": "Hello"
  }
}

Correct Webhook Data Access

❌ WRONG: {{$json.name}}
❌ WRONG: {{$json.email}}

✅ CORRECT: {{$json.body.name}}
✅ CORRECT: {{$json.body.email}}
✅ CORRECT: {{$json.body.message}}

Why: Webhook node wraps incoming data under .body property to preserve headers, params, and query parameters.

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Common Patterns

Access Nested Fields

// Simple nesting
{{$json.user.email}}

// Array access
{{$json.data[0].name}}
{{$json.items[0].id}}

// Bracket notation for spaces
{{$json['field name']}}
{{$json['user data']['first name']}}

Reference Other Nodes

// Node without spaces
{{$node["Set"].json.value}}

// Node with spaces (common!)
{{$node["HTTP Request"].json.data}}
{{$node["Respond to Webhook"].json.message}}

// Webhook node
{{$node["Webhook"].json.body.email}}

Combine Variables

// Concatenation (automatic)
Hello {{$json.body.name}}!

// In URLs
https://api.example.com/users/{{$json.body.user_id}}

// In object properties
{
  "name": "={{$json.body.name}}",
  "email": "={{$json.body.email}}"
}

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When NOT to Use Expressions

❌ Code Nodes

Code nodes use direct JavaScript access, NOT expressions!

// ❌ 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

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

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

❌ Credential Fields

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

// ✅ CORRECT
Use n8n credential system, not expressions

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Validation Rules

1. Always Use {{}}

Expressions must be wrapped in double curly braces.

❌ $json.field
✅ {{$json.field}}

2. Use Quotes for Spaces

Field or node names with spaces require bracket notation:

❌ {{$json.field name}}
✅ {