Free tool
CSV Cleanroom
Merge, deduplicate and standardize messy exports — then see exactly what changed.
- Private by design. Files are processed on your computer. This page is technically blocked from sending data anywhere.
- Nothing silent. Exact duplicates merge automatically; likely duplicates wait for your yes or no.
- Fully auditable. You get the cleaned file, an exceptions list, and a log of every change.
1 Add your files
Recommended up to ~50,000 rows per session (tested to 160,000 on a desktop browser).
2 Check the columns
We guessed what each column holds. Columns with the same Output column name are combined across files. Set Skip to leave a column out.
3 Review possible duplicates
4 Download
Undecided groups are kept as separate rows and listed in the exceptions file — nothing uncertain is merged without you.
Doing this every week?
If the same cleanup keeps coming back — or it needs to flow straight into QuickBooks, your CRM or a database — Merritt Stack builds that pipeline once and keeps it running.
Contact details coming soon.