Working with Data: Expressions and $json

Expressions Are n8n's Dynamic Values

In n8n, most node parameters accept either a fixed value (you type it in) or an expression — a small piece of code wrapped in double curly braces: {{ }}. Expressions let you pull in data from previous nodes, do light calculations, and format values dynamically at runtime.

To switch a field from a fixed value to an expression, click the field and look for the expression toggle (a small lightning bolt icon on the right). Once in expression mode, everything between {{ and }} is evaluated as JavaScript.

The $json Variable

$json is the most important variable in n8n expressions. It refers to the JSON data of the current item being processed. If a Google Sheets node returned a row with columns "Name", "Email", and "Company", you access those values as:

{{ $json.Name }}
{{ $json.Email }}
{{ $json.Company }}

You can navigate nested objects with dot notation: {{ $json.address.city }}. For array values, use bracket notation: {{ $json.tags[0] }}.

Referencing Other Nodes

By default, $json refers to the current item from the immediately preceding node. To reference data from a different node earlier in the workflow, use $('Node Name'):

{{ $('Google Sheets').item.json.Email }}

Replace "Google Sheets" with the exact name of the node you want to pull from. This is how you use data from a node that is not your direct predecessor — for example, referencing the original webhook payload after several transformation steps.

Built-in Variables

n8n provides several built-in variables available in every expression:

• $now — the current date and time as a Luxon DateTime object: {{ $now.toISO() }}
• $today — today's date at midnight: {{ $today.toFormat('yyyy-MM-dd') }}
• $workflow.id — the current workflow's ID
• $execution.id — the unique ID of the current execution run
• $itemIndex — the zero-based index of the current item in the list

Common Expression Patterns

Here are expressions you will use constantly:

• Concatenate strings: {{ $json.FirstName + ' ' + $json.LastName }}
• Format a date: {{ $now.toFormat('MMMM d, yyyy') }}
• Fallback value: {{ $json.nickname || $json.name }}
• Convert to lowercase: {{ $json.email.toLowerCase() }}
• Check a condition: {{ $json.status === 'active' ? 'Yes' : 'No' }}

The expression editor in n8n shows you a live preview of the result as you type — use it to verify your expression before running the workflow.