Diagnose CSV Row Structure in n8n: Form Upload Validator

Instantly diagnose broken CSV structure in n8n—get a validation report back as an annotated diagnostic CSV

This n8n workflow lets you upload a UTF-8, comma-delimited CSV via a web form, then analyzes the header and each row’s structure—returning an annotated diagnostic CSV with clear status, errors, and warnings to help you pinpoint what’s wrong fast.

What this workflow does

• Accepts a CSV upload through an n8n Form Trigger.
• Enforces a 1 MiB file size limit and verifies the uploaded content decodes as UTF-8.
• Parses the CSV and checks for header issues, row width (column count) mismatches, and quoting problems.
• Compares each data row’s column count to the header width, preserving any trailing extra cells and flagging mismatches as structural errors.
• Generates an annotated diagnostic CSV that adds columns such as:
  • source row
  • validation status
  • errors and warnings (including spreadsheet formula-prefix protection notes)
• If the upload contains at least one data row, the workflow returns the diagnostic CSV; otherwise, it shows a safe HTML error message using a safe file-level error path for unreadable/empty inputs.

Use cases

• Validate vendor-supplied CSVs before importing into your automation pipeline.
• Debug recurring parsing failures by quickly identifying rows with column-count drift or quoting issues.
• Give SaaS users a “downloadable CSV health report” during onboarding or bulk data uploads.

Technical details

• Built with Form Trigger, Form, Code, and IF nodes (plus a Sticky Note for operator guidance).
• Self-hosted setup targets n8n 2.40.7: import the workflow JSON, test via the Form Trigger URL, then validate downloads for both successful row diagnostics and safe file-level error handling.