This n8n template provides a simple yet powerful utility for validating if a given string input is a valid JSON format. You can use this to pre-validate data received from external sources, ensure data integrity before further processing, or provide immediate feedback to users submitting JSON strings.

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🔧 How it works

• Webhook: This node acts as the entry point for the workflow, listening for incoming POST requests. It expects a JSON body with a single property:

  • jsonString: The string that you want to validate as JSON.

• Code (JSON Validator): This node contains custom JavaScript code that attempts to parse the jsonString provided in the webhook body.

  • If the jsonString can be successfully parsed, it means it's valid JSON, and the node returns an item with valid: true.
  • If parsing fails, it catches the error and returns an item with valid: false and the specific error message.
  • This logic is applied to each item passed through the node, ensuring all inputs are validated.

• Respond to Webhook: This node sends the validation result (either valid: true or valid: false with an error message) back to the service that initiated the webhook request.

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👤 Who is it for?

This workflow is ideal for:

• Developers & Integrators: Pre-validate JSON payloads from external systems (APIs, webhooks) before processing them in your workflows, preventing errors.
• Data Engineers: Ensure the integrity of JSON data before storing it in databases or data lakes.
• API Builders: Offer a dedicated endpoint for clients to test their JSON strings for validity.
• Customer Support Teams: Quickly check user-provided JSON configurations for errors.
• Anyone handling JSON data: A quick and easy way to programmatically check JSON string correctness without writing custom code in every application.

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📑 Data Structure

When you trigger the webhook, send a POST request with a JSON body structured as follows:

{
  "jsonString": "{\"name\": \"n8n\", \"type\": \"workflow\"}"
}

Example of an invalid JSON string:

{
  "jsonString": "{name: \"n8n\"}" // Missing quotes around 'name'
}

The workflow will return a JSON response indicating validity:

For a valid JSON string:

{
  "valid": true
}

For an invalid JSON string:

{
  "valid": false,
  "error": "Unexpected token 'n', \"{name: \"n8n\"}\" is not valid JSON"
}

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⚙️ Setup Instructions

• Import Workflow:

  • In your n8n editor, click "Import from JSON" and paste the provided workflow JSON.

• Configure Webhook Path:

  • Double-click the Webhook node.
  • In the 'Path' field, set a unique and descriptive path (e.g., /validate-json).

• Activate Workflow:

  • Save and activate the workflow.

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📝 Tips

This JSON validator workflow is a solid starting point. Consider these enhancements:

• Enhanced Error Feedback:

  • Upgrade: Add a Set node after the Code node to format the error message into a more user-friendly string before responding.
  • Leverage: Make it easier for the caller to understand the issue.

• Logging Invalid Inputs:

  • Upgrade: After the Code node, add an IF node to check if valid is false. If so, branch to a node that logs the invalid jsonString and error to a Google Sheet, database, or a logging service.
  • Leverage: Track common invalid inputs for debugging or improvement.

• Transforming Valid JSON:

  • Upgrade: If the JSON is valid, you could add another Function node to parse the jsonString and then operate on the parsed JSON data directly within the workflow.
  • Leverage: Use this validator as the first step in a larger workflow that processes JSON data.

• Asynchronous Validation:

  • Upgrade: For very large JSON strings or high-volume requests, consider using a separate queueing mechanism (e.g., RabbitMQ, SQS) and an asynchronous response pattern.
  • Leverage: Prevent webhook timeouts and improve system responsiveness.