Original rows
0
CSV deduplicator by key columns
Remove duplicate CSV rows using key columns you choose. Keep the first row, keep the last row, or merge non-empty values.
Free to use with no signup. Processing stays in your browser, and input data is not stored.
Free, no signup
Processed in your browser
No data stored
Input CSV
Upload a file, paste CSV text, or try the sample.
Key Columns and Duplicate Rule
Select one or more key columns and choose which row to keep when duplicates are found.
Result (Preview, Metrics, Download)
Review the summary, then export deduplicated rows, duplicate-only rows, or a duplicate-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, or merge mode, run deduplication, and download the result
FAQ
Which row is kept when duplicates exist?
Choose first-win (keep the first row), last-win (keep the last row), or merge non-empty values. For merge conflicts, keep the first value, keep the last, or show a warning list.
Can I ignore letter case?
Yes. Change the letter-case option in Advanced settings, and it will be applied when keys are compared.
Can I see summary counts?
The result card shows original rows, rows after deduplication, removed rows, and duplicate-group count.
Can I select multiple key columns?
Yes. Rows are duplicates when the combination of values in the selected key columns matches.
My CSV looks garbled in Shift_JIS
Switch the file encoding between UTF-8 and Shift_JIS, then load the file again.
Why do I get zero duplicates?
Check the key columns, trimming, letter-case, and blank-key settings.
Notes
- Handle personal data in key columns carefully.
- When using merge mode, review conflicts before accepting the output.
- Column-count mismatches are often caused by an unclosed quote.