Free Tools /n8n
n8n Expression Tester
Paste sample data, write an n8n-style {{$json.field}} expression, and see exactly what it resolves to before pasting it into a real node.
- Free, no signup
- Runs in your browser
- Nothing stored
Resolved result
How this tool works
Simulates n8n's $json context
Paste sample input data as JSON, it becomes available as $json inside your expression, exactly like the current item in a real n8n node.
Supports common n8n expression syntax
Write {{$json.field}}, {{$json.nested.value}}, or a full JavaScript expression with $json in it, the same syntax n8n's expression editor accepts.
Shows the exact resolved value
See precisely what n8n would substitute into that field, including type, so you can catch a silent string-vs-number mismatch before it breaks a downstream IF node.
Frequently asked questions
Does this run the exact same engine as n8n?
It evaluates standard JavaScript expressions the same way the browser and Node.js do, which covers the overwhelming majority of n8n expressions. n8n-specific helper functions (like $now, $workflow, or $items() referencing other nodes) are not available here since they depend on live workflow context this tool cannot simulate.
Why does my expression return undefined here but work in n8n?
Most commonly because your sample JSON does not match the real shape of the data at that point in your workflow, check the exact field names and nesting against a real execution's input data in n8n's UI.
Can I test expressions that reference other nodes, like $node["NodeName"].json?
Not directly, since this tool only simulates a single item's $json context. For expressions referencing other nodes, test them inside n8n itself using the built-in expression preview, which has access to real workflow state.
What is the difference between {{ }} and a plain JavaScript expression in n8n?
{{ }} is n8n's expression syntax marking a field as dynamic rather than static text. Inside the braces, the content is evaluated as JavaScript. This tool accepts either the full {{$json.field}} syntax or the bare expression, both resolve the same way.
Can I chain multiple expressions in one field like n8n allows?
Yes, paste multiple {{ }} blocks in your input and the tool resolves each one independently, then shows the final combined string, matching how n8n concatenates multiple expression blocks within one field.
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