Original rows
0
CSV Deduplicator (Remove Duplicates by Key Columns)
Remove duplicate rows from CSV by selected key columns. Choose first-win, last-win, or merge non-empty values for practical deduplication.
No signup, free to use. Processing stays in your browser and data is not stored.
No signup / Free
Processed in browser
No data storage
Input CSV
Start from file upload, paste, or sample input.
Key Columns and Duplicate Rule
Select one or more key columns and choose how to keep rows when duplicates are found.
Result (Preview, Metrics, Download)
Review summary metrics and export deduplicated rows, duplicate-only rows, or group summary CSV.
How to use
- Upload a CSV file (or paste CSV text)
- Select the key columns used for duplicate detection
- Choose first/last/merge mode, run dedupe, and download the result
FAQ
Which row is kept when duplicates exist?
You can choose first-win (keep first row), last-win (keep last row), or merge non-empty values. For merge conflicts, choose first, last, or warning list.
Can I ignore letter case?
Yes. Switch the case option in advanced settings and it will be applied to key comparison.
Can I see summary counts?
The result card shows original rows, rows after dedupe, removed rows, and duplicate group count.
Can I select multiple key columns?
Yes. Rows are considered duplicates when the combination of selected key columns matches.
My CSV is garbled (Shift_JIS).
Switch encoding between UTF-8 and Shift_JIS, then reload the file.
Why do I get zero duplicates?
Check key column selection, trim setting, case setting, and blank-key handling.
Notes
- Handle personal data in key columns carefully.
- When using merge mode, review conflicts before finalizing output.
- Column mismatch errors are often caused by missing closing quotes.