Validates n8n expression syntax, fixes errors with {{}} format, $json/$node variables, webhook .body access, and common workflow patterns.
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Expert guide for writing correct n8n expressions in workflows.
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)
Access data from the current node:
{{$json.fieldName}}
{{$json['field with spaces']}}
{{$json.nested.property}}
{{$json.items[0].name}}
Access data from any previous node:
{{$node["Node Name"].json.fieldName}}
{{$node["HTTP Request"].json.data}}
{{$node["Webhook"].json.body.email}}
Important:
Access current date/time:
{{$now}}
{{$now.toFormat('yyyy-MM-dd')}}
{{$now.toFormat('HH:mm:ss')}}
{{$now.plus({days: 7})}}
Access environment variables:
{{$env.API_KEY}}
{{$env.DATABASE_URL}}
Most Common Mistake: Webhook data is NOT at the root!
{
"headers": {...},
"params": {...},
"query": {...},
"body": { // ⚠️ USER DATA IS HERE!
"name": "John",
"email": "john@example.com",
"message": "Hello"
}
}
❌ WRONG: {{$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.
// Simple nesting
{{$json.user.email}}
// Array access
{{$json.data[0].name}}
{{$json.items[0].id}}
// Bracket notation for spaces
{{$json['field name']}}
{{$json['user data']['first name']}}
// Node without spaces
{{$node["Set"].json.value}}
// Node with spaces (common!)
{{$node["HTTP Request"].json.data}}
{{$node["Respond to Webhook"].json.message}}
// Webhook node
{{$node["Webhook"].json.body.email}}
// Concatenation (automatic)
Hello {{$json.body.name}}!
// In URLs
https://api.example.com/users/{{$json.body.user_id}}
// In object properties
{
"name": "={{$json.body.name}}",
"email": "={{$json.body.email}}"
}
Code nodes use direct JavaScript access, NOT expressions!
// ❌ WRONG in Code node
const email = '={{$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 = $input.all();
// ❌ WRONG
path: "{{$json.user_id}}/webhook"
// ✅ CORRECT
path: "user-webhook" // Static paths only
// ❌ WRONG
apiKey: "={{$env.API_KEY}}"
// ✅ CORRECT
Use n8n credential system, not expressions
Expressions must be wrapped in double curly braces.
❌ $json.field
✅ {{$json.field}}
Field or node names with spaces require bracket notation:
❌ {{$json.field name}}
✅ {{$json['field name']}}
❌ {{$node.HTTP Request.json}}
✅ {{$node["HTTP Request"].json}}
Node references are case-sensitive:
❌ {{$node["http request"].json}} // lowercase
❌ {{$node["Http Request"].json}} // wrong case
✅ {{$node["HTTP Request"].json}} // exact match
Don't double-wrap expressions:
❌ {{{$json.field}}}
✅ {{$json.field}}
For complete error catalog with fixes, see COMMON_MISTAKES.md
| 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) | $json.email |
For real workflow examples, see EXAMPLES.md
Webhook receives:
{
"body": {
"name": "John Doe",
"email": "john@example.com",
"message": "Hello!"
}
}
In Slack node text field:
New form submission!
Name: {{$json.body.name}}
Email: {{$json.body.email}}
Message: {{$json.body.message}}
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}}
// Current date
{{$now.toFormat('yyyy-MM-dd')}}
// Result: 2025-10-20
// Time
{{$now.toFormat('HH:mm:ss')}}
// Result: 14:30:45
// Full datetime
{{$now.toFormat('yyyy-MM-dd HH:mm')}}
// Result: 2025-10-20 14:30
// First item
{{$json.users[0].email}}
// Array length
{{$json.users.length}}
// Last item
{{$json.users[$json.users.length - 1].name}}
// Dot notation (no spaces)
{{$json.user.email}}
// Bracket notation (with spaces or dynamic)
{{$json['user data'].email}}
// Concatenation (automatic)
Hello {{$json.name}}!
// String methods
{{$json.email.toLowerCase()}}
{{$json.name.toUpperCase()}}
// Direct use
{{$json.price}}
// Math operations
{{$json.price * 1.1}} // Add 10%
{{$json.quantity + 5}}
// Ternary operator
{{$json.status === 'active' ? 'Active User' : 'Inactive User'}}
// Default values
{{$json.email || 'no-email@example.com'}}
// Add days
{{$now.plus({days: 7}).toFormat('yyyy-MM-dd')}}
// Subtract hours
{{$now.minus({hours: 24}).toISO()}}
// Set specific date
{{DateTime.fromISO('2025-12-25').toFormat('MMMM dd, yyyy')}}
// Substring
{{$json.email.substring(0, 5)}}
// Replace
{{$json.message.replace('old', 'new')}}
// Split and join
{{$json.tags.split(',').join(', ')}}
"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
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()+, -, *, /, %.bodyEssential Rules:
.bodyMost Common Mistakes:
{{$json.name}} in webhooks → Use {{$json.body.name}}{{$json.email}} in Code → Use $json.email{{$node.HTTP Request}} → Use {{$node["HTTP Request"]}}For more details, see:
Need Help? Reference the n8n expression documentation or use n8n-mcp validation tools to check your expressions.