n8n Expression Syntax

All dynamic content in n8n uses double curly braces:

{{expression}}

// ✅ Valid expressions
{{$json.email}}
{{$json.body.name}}
{{$node["HTTP Request"].json.data}}

// ❌ Invalid — missing or wrong braces
$json.email       // treated as literal text
{$json.email}     // single braces — invalid

Webhook data is NOT at the root of $json.Webhook nodes wrap all incoming data under a .body property. Always access webhook fields as {{$json.body.fieldName}}, never {{$json.fieldName}}.

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

// ✅ CORRECT
{{$json.body.name}}
{{$json.body.email}}

Core Variables

`$json` — Current Node Output

Access data from the current node in the workflow:

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

`$node` — Reference Other Nodes

Access data from any previous node by name:

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

Node names must be in quotes inside brackets. Node names are case-sensitive and must match the exact name in your workflow.

`$now` — Current Timestamp

Access and format the current date/time using Luxon:

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

`$env` — Environment Variables

Access n8n environment variables:

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

Webhook Data Structure

The webhook node wraps all incoming request data:

// Full $json structure from a Webhook node
{
  "headers": {"content-type": "application/json"},
  "params":  {},
  "query":   {},
  "body": {              // ⚠️ User data is HERE
    "name": "John",
    "email": "john@example.com",
    "message": "Hello"
  }
}

In a Slack node text field after a Webhook:

New form submission!

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

Common Patterns

Nested Fields

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

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

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

Combining Variables

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

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

// In JSON parameters
{
  "name": "={{$json.body.name}}",
  "email": "={{$json.body.email}}"
}

Multi-Node Data Flow

// Reference previous node by name
{{$node["Webhook"].json.body.order_id}}
{{$node["HTTP Request"].json.data.items[0].name}}

When NOT to Use Expressions

Do not use {{}} expressions inside Code nodes. Code nodes use direct JavaScript/Python — the {{}} syntax is for expression fields in other node types only.

Code Nodes
Webhook Paths
Credential Fields

// ❌ 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 the $input API
const email = $input.item.json.email;
const allItems = $input.all();

// ❌ WRONG — webhook paths must be static
path: "{{$json.user_id}}/webhook"

// ✅ CORRECT — use static paths
path: "user-webhook"

// For dynamic parameters, use URL path params instead
path: "user-webhook/:userId"

// ❌ WRONG — credentials use n8n's credential system
apiKey: "={{$env.API_KEY}}"

// ✅ CORRECT
// Configure API keys through the Credentials section, not parameters

Data Type Handling

Arrays
Objects
Strings
Numbers

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

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

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

// Join all emails
{{$json.users.map(u => u.email).join(', ')}}

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

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

// Auto-concatenation
Hello {{$json.name}}!

// String methods
{{$json.email.toLowerCase()}}
{{$json.name.toUpperCase()}}
{{$json.message.trim()}}
{{$json.message.replace('old', 'new')}}

// 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'}}

// Multiple conditions
{{$json.order.total > 100 ? 'Premium Customer' : 'Standard Customer'}}

Date Manipulation

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

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

// Specific date formatting
{{DateTime.fromISO('2025-12-25').toFormat('MMMM dd, yyyy')}}
// Result: December 25, 2025

String Manipulation

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

// Replace
{{$json.message.replace('World', 'n8n')}}

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

Common Mistakes Quick Reference

Mistake	Fix
`$json.field`	`{{$json.field}}`
`{{$json.field name}}`	`{{$json['field name']}}`
`{{$node.HTTP Request}}`	`{{$node["HTTP Request"]}}`
`{{{$json.field}}}`	`{{$json.field}}`
`{{$json.name}}` (from webhook)	`{{$json.body.name}}`
`'={{$json.email}}'` (in Code node)	`$json.email`
`{{$json.items.0.name}}`	`{{$json.items[0].name}}`
`Hello ${$json.name}` (template literal)	`Hello {{$json.name}}`
`{{$node["HTTP Request"].data}}`	`{{$node["HTTP Request"].json.data}}`

Complete Error Catalog

Missing curly braces

Symptom: Field shows literal text like $json.email instead of the actual value.

❌ $json.email
✅ {{$json.email}}

Webhook body access

Symptom: Undefined values when accessing webhook data even though the data is being sent.

// Webhook structure:
{
  "headers": {...},
  "params": {},
  "query": {},
  "body": { "name": "John" }  // Data is HERE
}

// Fix:
❌ {{$json.name}}
✅ {{$json.body.name}}

Spaces in field names

Symptom: Syntax error or undefined when the field definitely exists.

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

❌ {{$json.user data.email}}
✅ {{$json['user data'].email}}

Spaces in node names

Symptom: Error like "Cannot read property 'Request' of undefined".

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

Wrong node name case

Symptom: Undefined value even though the node exists and has data.

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

Double wrapping

Symptom: Output shows {{value}} instead of the actual value.

❌ {{{$json.field}}}
✅ {{$json.field}}

Array access with dots

Symptom: Syntax error or undefined.

❌ {{$json.items.0.name}}
✅ {{$json.items[0].name}}

Using = prefix outside JSON mode

Symptom: Output shows =john@example.com instead of john@example.com.

// In text fields (no = needed)
❌ Email: ={{$json.email}}
✅ Email: {{$json.email}}

// In JSON mode (= IS needed to set whole value to expression)
{
  "email": "={{$json.body.email}}"
}

Missing .json in $node reference

Symptom: Undefined value when you know the node has data.

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

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

Debugging Expressions

Open the expression editor

Click the field containing the expression, then click the fx icon to open the expression editor.

Check the live preview

The expression editor shows a live preview of the result. Check for values appearing as undefined or error messages 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” → Calling a method on the wrong type; check the variable type
Expression shows as literal text → Missing {{ }}; add curly braces

Follow the debugging checklist

Is it wrapped in {{ }}?
Is it webhook data? Add .body
Does the field or node name have spaces? Use bracket notation
Does the node name case match exactly?
Is the property path correct? Check the data structure in the editor
Is this inside a Code node? Remove {{ }}

Expression Helper Reference

Type	Available Methods
String	`.toLowerCase()`, `.toUpperCase()`, `.trim()`, `.replace()`, `.substring()`, `.split()`, `.includes()`
Array	`.length`, `.map()`, `.filter()`, `.find()`, `.join()`, `.slice()`, `.reduce()`
DateTime (Luxon)	`.toFormat()`, `.toISO()`, `.toLocal()`, `.plus()`, `.minus()`, `.set()`
Number	`.toFixed()`, `.toString()`, `+`, `-`, `*`, `/`, `%`

Best Practices

Do

Always use {{ }} for dynamic content
Use bracket notation for field names with spaces
Access webhook data from .body
Use $node to reference data from earlier nodes
Test expressions in the expression editor

Don't

Use {{ }} inside Code nodes
Forget quotes around node names with spaces
Double-wrap with extra {{ }}
Assume webhook data is at the root
Use expressions in webhook paths or credential fields

​n8n Expression Syntax

​Core Variables

​$json — Current Node Output

​$node — Reference Other Nodes

​$now — Current Timestamp

​$env — Environment Variables

​Webhook Data Structure

​Common Patterns

​Nested Fields

​Combining Variables

​Multi-Node Data Flow

​When NOT to Use Expressions

​Data Type Handling

​Advanced Patterns

​Conditional Content

​Date Manipulation

​String Manipulation

​Common Mistakes Quick Reference

​Complete Error Catalog

​Debugging Expressions

​Expression Helper Reference

​Best Practices

Do

Don't

n8n Expression Syntax

Core Variables

`$json` — Current Node Output

`$node` — Reference Other Nodes

`$now` — Current Timestamp

`$env` — Environment Variables

Webhook Data Structure

Common Patterns

Nested Fields

Combining Variables

Multi-Node Data Flow

When NOT to Use Expressions

Data Type Handling

Advanced Patterns

Conditional Content

Date Manipulation

String Manipulation

Common Mistakes Quick Reference

Complete Error Catalog

Debugging Expressions

Expression Helper Reference

Best Practices