✅ n8n Expression Tester

Free n8n Expression Validator - Test Before You Deploy

Validate expression syntax and preview results without running your workflow.

Syntax Check

Live Preview

Error Detection

Try Free Expression Validator

What Are n8n Expressions?

n8n expressions are JavaScript-like code snippets wrapped in {{ }} that dynamically reference data from previous nodes. They let you access input data, transform values, and create conditional logic. For example, {{ $json.email }} accesses an email field, while {{ $json.price * 1.1 }} calculates a 10% markup. Expressions are powerful but syntax errors are common.

Why Expression Errors Are the #1 n8n Frustration

Expression errors account for the majority of n8n workflow failures. Common issues include referencing undefined fields, syntax errors like trailing periods, and type mismatches. These errors often only appear at runtime, causing workflows to fail unexpectedly. Validating expressions before deployment saves hours of debugging.

n8n Expression Best Practices

Always use optional chaining: {{ $json.user?.email }} to handle missing data
Test expressions with the expression editor's preview feature
Use $if() for conditional values instead of complex ternary operators
Reference specific items with $('NodeName').item.json when needed
Avoid trailing periods or incomplete property access
Use JSON.stringify() to debug complex objects

Frequently Asked Questions

What n8n expression syntax does this validator support?

The validator supports all n8n expression syntax including $json, $input, $('NodeName'), $if(), $now, and JavaScript operations. It validates both simple property access like {{ $json.email }} and complex expressions with methods and conditionals.

Why do I need to validate expressions separately?

Expression errors are the #1 cause of n8n workflow failures. Testing expressions in isolation catches syntax errors, undefined references, and type mismatches before they break your workflow in production. It's faster than running the full workflow to test.

How do I provide sample data for testing?

Paste valid JSON in the 'Sample Input Data' field that represents what the previous node would output. For example, if testing {{ $json.user.email }}, provide {"user": {"email": "test@example.com"}}. This lets the validator preview actual results.

What does 'undefined' in the result mean?

If your expression result shows 'undefined', it means the property path doesn't exist in your sample data. Check for typos in property names or use optional chaining ({{ $json.user?.email }}) to handle missing data gracefully.

Is this tool free?

Yes, completely free with no signup required. We built this to help n8n users avoid the frustration of expression errors. For complex expression logic or workflow development help, we offer professional services.

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