Would you upload a customer CSV to remove duplicates?

Customer and CRM exports are exactly where an upload-first cleaner can become uncomfortable. Before using any CSV cleanup tool, I would check five things:

1. Where is the file processed and retained?

2. Can I review duplicate groups before deleting anything?

3. Does it distinguish exact duplicates from similar names or emails?

4. Can I undo edits and keep the original untouched?

5. What happens when the file is too large for the browser?

Disclosure: I built CSV Repair & Deduper around that checklist. It is one HTML file that runs locally in your browser, repairs common delimiter, encoding, and row-shape issues, and lets you review exact and near-duplicate groups before export. It is a $19 one-time purchase, not a subscription. Very large files can still be slow, and exported results should always be reviewed before import.

Product and working demo: https://store.marabusiness.net/store/csv-repair-deduper?utm_source=producthunt&utm_medium=forum&utm_content=csv-privacy-question

For people who regularly handle CRM or ecommerce exports: which matters more in practice: no-upload privacy, catching near-duplicates, or previewing every change?