If you have ever copy-pasted the same value into a dozen nodes, you already know the pain. n8n expressions are the fix. They let you pull live data from any previous node, do math, format dates, and build strings in any field in your workflow.
This post covers everything you need to get moving: syntax, the most useful built-in variables, and real-world examples you can drop into your own workflows.
What Is an n8n Expression?
An expression is JavaScript wrapped in double curly braces.
Whenever n8n sees those braces in a field, it evaluates what is inside and uses the result.
Example: {{ $json.email }} grabs the email field from the current item. No node. No extra step. Just live data.
How to Open the Expression Editor
- Hover over any input field in a node.
- Click the = icon that appears on the right.
- The field turns purple, you are now in expression mode.
- Type your expression. The preview pane at the bottom shows the live result.
The Core Variables
$json - current item data
$json.name- simple field
$json.order.total- nested field
$json.items[0].sku- array element
$json is the data object of the current item being processed.
$('Node Name').item.json - data from a specific node
Pull data from any previous node by name. This is the most powerful pattern.
Example: $('HTTP Request').item.json.id or $('Get User').item.json.profile.avatar_url
$now - current timestamp (Luxon DateTime)
$now.toISO()- full ISO string
$now.toFormat('yyyy-MM-dd')- formatted date
$now.minus({ days: 7 }).toISO()- one week ago
$vars - workflow variables (n8n 1.x+)
Set static values once in Settings > Variables and reference them everywhere.
$vars.SLACK_CHANNEL$vars.API_BASE_URL
$env - environment variables (self-hosted only)
$env.MY_SECRET_KEY
JavaScript Is Fair Game
Everything inside {{ }} is evaluated as JavaScript:
// String methods
{{ $json.name.toUpperCase() }}
{{ $json.email.split('@')[0] }}
// Ternary
{{ $json.status === 'active' ? 'Active' : 'Inactive' }}
// Math
{{ $json.price * 1.2 }}
// Array length
{{ $json.items.length }}
Practical Examples
1. Dynamic email subject
Order confirmed for {{ $json.customer_name }}
2. Format date for Google Sheets
{{ $now.toFormat('MM/dd/yyyy') }}
3. Combine names
{{ $json.first_name + ' ' + $json.last_name }}
4. Safely handle a missing field
{{ $json.middle_name ?? 'N/A' }}
The ?? nullish coalescing operator returns N/A if the field is null or undefined.
5. Pull data from a different branch
In a Merge node after two parallel branches:
Customer: {{ $('Get Customer').item.json.name }}
Order total: {{ $('Get Order').item.json.total }}
6. Build a URL dynamically
https://api.example.com/users/{{ $json.user_id }}/orders/{{ $json.order_id }}
Paste directly into the URL field of an HTTP Request node.
Common Mistakes
| Mistake | Fix |
|---|---|
json.name missing $ | Use $json.name |
| Spaces inside braces | {{ $json.name }} not { {$json.name} } |
| Wrong node name casing | Names are case-sensitive |
| Array without index | Use $json.items[0] not $json.items |
| Expression in static field | Click = icon to switch to expression mode |
Free Workflow JSON
Here is a minimal workflow demonstrating four expression patterns - dynamic URL, formatted date, ternary condition, and name concat:
{
"name": "n8n Expressions Demo",
"nodes": [
{
"parameters": {},
"name": "Start",
"type": "n8n-nodes-base.manualTrigger",
"typeVersion": 1,
"position": [240, 300]
},
{
"parameters": {
"values": {
"string": [
{ "name": "user_id", "value": "42" },
{ "name": "status", "value": "active" },
{ "name": "first_name", "value": "Ada" },
{ "name": "last_name", "value": "Lovelace" }
]
}
},
"name": "Set Sample Data",
"type": "n8n-nodes-base.set",
"typeVersion": 1,
"position": [460, 300]
},
{
"parameters": {
"values": {
"string": [
{ "name": "full_name", "value": "={{ $json.first_name + ' ' + $json.last_name }}" },
{ "name": "api_url", "value": "=https://api.example.com/users/{{ $json.user_id }}" },
{ "name": "label", "value": "={{ $json.status === 'active' ? 'Active' : 'Inactive' }}" },
{ "name": "today", "value": "={{ $now.toFormat('yyyy-MM-dd') }}" }
]
}
},
"name": "Build Expressions",
"type": "n8n-nodes-base.set",
"typeVersion": 1,
"position": [680, 300]
}
],
"connections": {
"Start": { "main": [[{ "node": "Set Sample Data", "type": "main", "index": 0 }]] },
"Set Sample Data": { "main": [[{ "node": "Build Expressions", "type": "main", "index": 0 }]] }
}
}
Import it into n8n, run it once, and inspect the output of Build Expressions to see all four patterns live.
Want More Ready-to-Run Workflows?
The patterns above power every automation I build. If you want a full library of production-ready workflows - error handling, webhooks, Stripe receipts, CRM sync, and more - I packaged them into the n8n Workflow Starter Pack ($29).
One purchase, instant download, no subscription.
Quick Reference
| Variable | What it gives you |
|---|---|
$json.field | Field from the current item |
$('Node Name').item.json.field | Field from a named previous node |
$now | Current time (Luxon DateTime) |
$vars.NAME | Workflow variable |
$env.NAME | Environment variable (self-hosted) |
$input.all() | All items entering the current node |
$input.first().json | First item only |
$input.last().json | Last item only |
Expressions unlock the difference between a rigid script and a truly dynamic workflow. Once they click, you will use them in every single node.
Drop a question below if you get stuck on a specific expression - happy to help debug it.
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