n8n Webhook Lead Validation & Dedup to Google Sheets

Automatically validate and deduplicate webhook leads into Google Sheets with n8n

This n8n workflow receives lead data via a webhook, normalizes and validates key fields, and then writes only valid, non-duplicate leads to your Google Sheets “Records” tab—while routing invalid submissions to a separate “Review Queue” tab for quick follow-up.

What this workflow does

• Receives lead data via Webhook (POST): The workflow exposes an “intake” webhook endpoint and expects a JSON payload.
• Normalizes incoming fields: It trims and lowercases the email (when provided) and adds a “received” timestamp.
• Validates required fields: It checks for a correctly formatted email address and a non-empty id (source ID).
• Routes invalid payloads to Google Sheets: If validation fails, the workflow appends the submission to the “Review Queue” sheet, including the failure reason and original values.
• Deduplicates by source ID: It looks up the provided source ID in the “Records” sheet. If a row with the same source_id already exists, the workflow skips creating a new record.
• Creates new records only when unique: If no matching source_id is found, it appends a new row to “Records”.

Use cases

• Capture leads from a web form or SaaS event and ensure Google Sheets stays clean.
• Prevent duplicate lead entries by enforcing uniqueness using id as source_id.
• Queue malformed submissions (missing email/source ID) for manual review without breaking your pipeline.

Technical details

• n8n Webhook (intake endpoint) to receive JSON payloads.
• Google Sheets integration using an OAuth2 credential to write to two tabs: “Records” and “Review Queue”.
• Workflow logic using nodes such as if, set, and no op (plus supporting nodes like sticky note for clarity).
• Requires your spreadsheet to include a source_id column in the Records tab for lookups.

Setup is straightforward: configure Google Sheets OAuth, set your REPLACE_WITH_YOUR_SPREADSHEET_ID, and POST JSON to the webhook with at least id (source ID) and email (optionally name).