n8n Expression Syntax

Expert guide for writing correct n8n expressions in workflows.

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: 14:30:45

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

Data Type Handling

Arrays

// First item {{$json.users[0].email}}

// Array length {{$json.users.length}}

// Last item {{$json.users[$json.users.length - 1].name}}

Objects

// Dot notation (no spaces) {{$json.user.email}}

// Bracket notation (with spaces or dynamic) {{$json['user data'].email}}

Strings

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

// String methods {{$json.email.toLowerCase()}} {{$json.name.toUpperCase()}}

Numbers

// Direct use {{$json.price}}

// Math operations {{$json.price * 1.1}} // Add 10% {{$json.quantity + 5}}

Advanced Patterns

Conditional Content

// Ternary operator {{$json.status === 'active' ? 'Active User' : 'Inactive User'}}

// Default values {{$json.email || 'no-email@example.com'}}

Date Manipulation

// Add days {{$now.plus({days: 7}).toFormat('yyyy-MM-dd')}}

// Subtract hours {{$now.minus({hours: 24}).toISO()}}

// Set specific date {{DateTime.fromISO('2025-12-25').toFormat('MMMM dd, yyyy')}}

String Manipulation

// Substring {{$json.email.substring(0, 5)}}

// Replace {{$json.message.replace('old', 'new')}}

// Split and join {{$json.tags.split(',').join(', ')}}

Debugging Expressions

Test in Expression Editor

• Click field with expression

• Open expression editor (click "fx" icon)

• See live preview of result

• Check for errors highlighted in red

Common Error Messages

"Cannot read property 'X' of undefined" → Parent object doesn't exist → Check your data path

"X is not a function" → Trying to call method on non-function → Check variable type

Expression shows as literal text → Missing {{ }} → Add curly braces

Expression Helpers

Available Methods

String:

• .toLowerCase() , .toUpperCase()

• .trim() , .replace() , .substring()

• .split() , .includes()

Array:

• .length , .map() , .filter()

• .find() , .join() , .slice()

DateTime (Luxon):

• .toFormat() , .toISO() , .toLocal()

• .plus() , .minus() , .set()

Number:

• .toFixed() , .toString()

• Math operations: + , - , * , / , %

Best Practices

✅ Do

• Always use {{ }} for dynamic content

• Use bracket notation for field names with spaces

• Reference webhook data from .body

• Use $node for data from other nodes

• Test expressions in expression editor

❌ Don't

• Don't use expressions in Code nodes

• Don't forget quotes around node names with spaces

• Don't double-wrap with extra {{ }}

• Don't assume webhook data is at root (it's under .body!)

• Don't use expressions in webhook paths or credentials

Related Skills

• n8n MCP Tools Expert: Learn how to validate expressions using MCP tools

• n8n Workflow Patterns: See expressions in real workflow examples

• n8n Node Configuration: Understand when expressions are needed

Summary

Essential Rules:

• Wrap expressions in {{ }}

• Webhook data is under .body

• No {{ }} in Code nodes

• Quote node names with spaces

• Node names are case-sensitive

Most Common Mistakes:

• Missing {{ }} → Add braces

• {{$json.name}} in webhooks → Use {{$json.body.name}}

• {{$json.email}} in Code → Use $json.email

• {{$node.HTTP Request}} → Use {{$node["HTTP Request"]}}

For more details, see:

• COMMON_MISTAKES.md - Complete error catalog

• EXAMPLES.md - Real workflow examples

Need Help? Reference the n8n expression documentation or use n8n-mcp validation tools to check your expressions.