/n8n-expression-syntax

name: n8n-expression-syntax
description: Validate n8n expression syntax and fix common errors. Use when writing n8n expressions, using {{}} syntax, accessing $json/$node variables, troubleshooting expression errors, or working with webhook data in workflows.
risk: unknown
source: community

n8n Expression Syntax

Expert guide for writing correct n8n expressions in workflows.

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.

---

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)

---

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}}

---

🚨 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": "john@example.com",
    "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.

---

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}}"
}

---

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

---

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**:

❌ {{$json.field name}}
✅ {{$json['field name']}}

❌ {{$node.HTTP Request.json}}
✅ {{$node["HTTP Request"].json}}

3. Match Exact Node Names

Node references are **case-sensitive**:

❌ {{$node["http request"].json}}  // lowercase
❌ {{$node["Http Request"].json}}  // wrong case
✅ {{$node["HTTP Request"].json}}  // exact match

4. No Nested {{}}

Don't double-wrap expressions:

❌ {{{$json.field}}}
✅ {{$json.field}}

---

Common Mistakes

For complete error catalog with fixes, see COMMON_MISTAKES.md

Quick Fixes

| Mistake | Fix | |---------|-----| | `$json.field` | `{{$json.field}}` | | `{{$json.field name}}` | `{{$json['field name']}}` | | `{{$node.HTTP Request}}` | `{{$node["HTTP Request"]}}` | | `{{{$json.field}}}` | `{{$json.field}}` | | `{{$json.name}}` (webhook) | `{{$json.body.name}}` | | `'={{$json.email}}'` (Code node) | `$json.email` |

---

Working Examples

For real workflow examples, see EXAMPLES.md

Example 1: Webhook to Slack

**Webhook receives**:

{
  "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**:

{
  "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

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

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