> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/czlonkowski/n8n-skills/llms.txt
> Use this file to discover all available pages before exploring further.
# n8n Expression Syntax
> Complete guide to writing correct n8n expressions: `{{}}` syntax, core variables, webhook data structure, common mistakes, and advanced patterns.
# n8n Expression Syntax
All dynamic content in n8n uses **double curly braces**:
```javascript theme={null}
{{expression}}
```
```javascript theme={null}
// ✅ 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 `{{$json.fieldName}}`.
```javascript theme={null}
// ❌ WRONG
{{$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:
```javascript theme={null}
{{$json.fieldName}}
{{$json['field with spaces']}}
{{$json.nested.property}}
{{$json.items[0].name}}
```
### `$node` — Reference Other Nodes
Access data from any previous node by name:
```javascript theme={null}
{{$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.
### `$now` — Current Timestamp
Access and format the current date/time using Luxon:
```javascript theme={null}
{{$now}}
{{$now.toFormat('yyyy-MM-dd')}}
{{$now.toFormat('HH:mm:ss')}}
{{$now.plus({days: 7})}}
```
### `$env` — Environment Variables
Access n8n environment variables:
```javascript theme={null}
{{$env.API_KEY}}
{{$env.DATABASE_URL}}
```
## Webhook Data Structure
The webhook node wraps all incoming request data:
```javascript theme={null}
// Full $json structure from a Webhook node
{
"headers": {"content-type": "application/json"},
"params": {},
"query": {},
"body": { // ⚠️ User data is HERE
"name": "John",
"email": "john@example.com",
"message": "Hello"
}
}
```
**In a Slack node text field after a Webhook:**
```text theme={null}
New form submission!
Name: {{$json.body.name}}
Email: {{$json.body.email}}
Message: {{$json.body.message}}
```
## Common Patterns
### Nested Fields
```javascript theme={null}
// 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']}}
{{$json['user data']['first name']}}
```
### Combining Variables
```javascript theme={null}
// Inline concatenation (automatic)
Hello {{$json.body.name}}!
// In URLs
https://api.example.com/users/{{$json.body.user_id}}
// In JSON parameters
{
"name": "={{$json.body.name}}",
"email": "={{$json.body.email}}"
}
```
### Multi-Node Data Flow
```javascript theme={null}
// Reference previous node by name
{{$node["Webhook"].json.body.order_id}}
{{$node["HTTP Request"].json.data.items[0].name}}
```
## When NOT to Use Expressions
**Do not use `{{}}` expressions inside Code nodes.** Code nodes use direct JavaScript/Python — the `{{}}` syntax is for expression fields in other node types only.
```javascript theme={null}
// ❌ WRONG in Code node
const email = '={{$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 = $input.all();
```
```javascript theme={null}
// ❌ WRONG — webhook paths must be static
path: "{{$json.user_id}}/webhook"
// ✅ CORRECT — use static paths
path: "user-webhook"
// For dynamic parameters, use URL path params instead
path: "user-webhook/:userId"
```
```javascript theme={null}
// ❌ WRONG — credentials use n8n's credential system
apiKey: "={{$env.API_KEY}}"
// ✅ CORRECT
// Configure API keys through the Credentials section, not parameters
```
## Data Type Handling
```javascript theme={null}
// First item
{{$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(', ')}}
```
```javascript theme={null}
// Dot notation (no spaces)
{{$json.user.email}}
// Bracket notation (spaces or dynamic keys)
{{$json['user data'].email}}
```
```javascript theme={null}
// Auto-concatenation
Hello {{$json.name}}!
// String methods
{{$json.email.toLowerCase()}}
{{$json.name.toUpperCase()}}
{{$json.message.trim()}}
{{$json.message.replace('old', 'new')}}
```
```javascript theme={null}
// Direct use
{{$json.price}}
// Math operations
{{$json.price * 1.1}} // Add 10%
{{$json.quantity + 5}}
```
## Advanced Patterns
### Conditional Content
```javascript theme={null}
// Ternary operator
{{$json.status === 'active' ? 'Active User' : 'Inactive User'}}
// Default values
{{$json.email || 'no-email@example.com'}}
// Multiple conditions
{{$json.order.total > 100 ? 'Premium Customer' : 'Standard Customer'}}
```
### Date Manipulation
```javascript theme={null}
// Add days
{{$now.plus({days: 7}).toFormat('yyyy-MM-dd')}}
// Subtract hours
{{$now.minus({hours: 24}).toISO()}}
// Specific date formatting
{{DateTime.fromISO('2025-12-25').toFormat('MMMM dd, yyyy')}}
// Result: December 25, 2025
```
### String Manipulation
```javascript theme={null}
// Substring
{{$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}}` | `{{$node["HTTP Request"].json.data}}` |
## Complete Error Catalog
**Symptom**: Field shows literal text like `$json.email` instead of the actual value.
```text theme={null}
❌ $json.email
✅ {{$json.email}}
```
**Symptom**: Undefined values when accessing webhook data even though the data is being sent.
```javascript theme={null}
// Webhook structure:
{
"headers": {...},
"params": {},
"query": {},
"body": { "name": "John" } // Data is HERE
}
// Fix:
❌ {{$json.name}}
✅ {{$json.body.name}}
```
**Symptom**: Syntax error or undefined when the field definitely exists.
```javascript theme={null}
❌ {{$json.first name}}
✅ {{$json['first name']}}
❌ {{$json.user data.email}}
✅ {{$json['user data'].email}}
```
**Symptom**: Error like `"Cannot read property 'Request' of undefined"`.
```javascript theme={null}
❌ {{$node.HTTP Request.json.data}}
✅ {{$node["HTTP Request"].json.data}}
```
**Symptom**: Undefined value even though the node exists and has data.
```javascript theme={null}
❌ {{$node["http request"].json.data}} // lowercase
❌ {{$node["Http Request"].json.data}} // wrong case
✅ {{$node["HTTP Request"].json.data}} // exact match
```
**Symptom**: Output shows `{{value}}` instead of the actual value.
```javascript theme={null}
❌ {{{$json.field}}}
✅ {{$json.field}}
```
**Symptom**: Syntax error or undefined.
```javascript theme={null}
❌ {{$json.items.0.name}}
✅ {{$json.items[0].name}}
```
**Symptom**: Output shows `=john@example.com` instead of `john@example.com`.
```javascript theme={null}
// In text fields (no = needed)
❌ Email: ={{$json.email}}
✅ Email: {{$json.email}}
// In JSON mode (= IS needed to set whole value to expression)
{
"email": "={{$json.body.email}}"
}
```
**Symptom**: Undefined value when you know the node has data.
```javascript theme={null}
❌ {{$node["HTTP Request"].data}} // Missing .json
✅ {{$node["HTTP Request"].json.data}}
❌ {{$node["Webhook"].body.email}} // Missing .json
✅ {{$node["Webhook"].json.body.email}}
```
## Debugging Expressions
Click the field containing the expression, then click the **fx** icon to open the expression editor.
The expression editor shows a live preview of the result. Check for values appearing as `undefined` or error messages highlighted in red.
* **"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
1. Is it wrapped in `{{ }}`?
2. Is it webhook data? Add `.body`
3. Does the field or node name have spaces? Use bracket notation
4. Does the node name case match exactly?
5. Is the property path correct? Check the data structure in the editor
6. 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
* 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
* 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