Remove duplicate CSV rows online free
Choose the columns that define a duplicate, preview the cleanup, and download both the cleaned CSV and removed rows.
Remove duplicate rows from one CSV entirely in your browser, without uploading the file, up to 500 MB. Choose one or more columns as the duplicate key, then keep either the first or last matching row in original source order; you can download both the cleaned CSV and the removed rows. The cap is correctness-verified, but processing time depends heavily on data shape: exports with millions of distinct key values can run roughly 100× slower than files with few distinct keys, so file size alone does not predict how long the cleanup will take.
Duplicate cleanup workspace
Choose the columns that define one record, then keep the first or last occurrence.
Results will appear here
Add valid data in the workspace above to preview and download the result.
Remove duplicates without losing the right record
- 1
Choose one CSV file from your device.
- 2
Choose one or more columns for duplicate matching.
- 3
Keep the first or last occurrence.
- 4
Review the duplicate groups and cleaned preview.
- 5
Download the cleaned file or removed rows.
Built for the real task
- Multi-column matching
- Keep first or last
- Removed-row export
- Local processing
See the transformation
Repeated records become a reviewable clean file.
Repeated rows are removed from the clean file and kept easy to review.
✓ Clean file keeps one copy
Browser limits
Files are limited to 500 MB to protect browser stability, especially on phones. Processing stays on this device.
Choose the columns that define a duplicate, preview the cleanup, and download both the cleaned CSV and removed rows.
The selected file is not uploaded to Nablyx.
No. This tool reads and transforms the file locally in your browser.
Common uses
- Multi-column matching
- Keep first or last
- Removed-row export
- Local processing
What counts as a duplicate?
Rows are duplicates when every selected key column has the same trimmed value. Choose an ID for exact duplicates or combine fields such as email and company.
Related guide
Related tools
Continue with a related Nablyx tool.
- Clean and fix CSV files — no uploadRepair common CSV problems including wrong delimiters, uneven rows, empty lines, whitespace, BOM markers, and duplicate headers.
- CSV column mapper and renamerRename, reorder, and remove CSV columns before importing data into a CRM, store, database, or accounting system — without uploading your file.
- Compare CSV files online freeCompare two CSV files and review added, removed, and changed rows directly in your browser.
Ready to work on your file?
Return to the workspace and process it locally.