CSV Deduplicator (Remove duplicate rows by key columns)

Q: "Which row is kept when duplicates exist?"

"Choose from keep first, keep last, or merge non-empty values. When merging, you can keep first/last values or list conflicts."

Q: "Can I ignore case?"

"Yes. Toggle case sensitivity under Advanced settings (applies to key comparison)."

Q: "Can I see counts for the whole result?"

"The results show original rows, rows after dedupe, removed rows, and duplicate group count."

Q: "Can I select multiple key columns?"

"Yes. The combination of selected columns defines duplicates."

Q: "My CSV is Shift_JIS and looks broken"

"Switch encoding to UTF-8 or Shift_JIS and re-load the file."

Q: "I got zero duplicates"

"Check your key column choices and settings for empty keys or case sensitivity."

Remove duplicate rows by key columns. Keep first/last or merge non-empty values for light record linkage.

Free No signup Runs in your browser

Your data stays in this browser and is never uploaded.

Input CSV

Input options

Input method

Drag & drop CSV here

or choose a file

Accepts .csv / .tsv

First row is header Delimiter Nag-e-encode

Preview (first 50 rows)

Scroll horizontally for wide tables.

Key columns & duplicate rules

Select key columns

Rows with the same combination of selected columns are treated as duplicates.

Which row do you keep?

Keep first Keep the first row in each group Keep last Keep the last row in each group Merge non-empty values Combine rows and fill blanks into one record

Advanced settings (optional)

Case sensitivity: Trim spaces: 保存 Normalize variants: do not

Empty key handling:

treat empty as a key do not dedupe empty keys

Target: 0 rows / Key columns: 0

Results (preview, counts, download)

Original rows 0

Rows after dedupe 0

Removed rows 0

Duplicate groups 0

I-download

Top 5 duplicate keys

Preview

Conflicts

使い方

Upload a CSV (or paste).
Choose key columns used for duplicate matching.
Pick keep-first/keep-last/merge, then run and download.

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Processing happens in your browser only (no server upload).
Large CSV files may take time to parse and dedupe.
If you see garbled text, switch encoding between UTF-8 and Shift_JIS and re-load.

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Q

Which row is kept when duplicates exist?

Choose from keep first, keep last, or merge non-empty values. When merging, you can keep first/last values or list conflicts.

Q

Can I ignore case?

Yes. Toggle case sensitivity under Advanced settings (applies to key comparison).

Q

Can I see counts for the whole result?

The results show original rows, rows after dedupe, removed rows, and duplicate group count.

Q

Can I select multiple key columns?

Yes. The combination of selected columns defines duplicates.

Q

My CSV is Shift_JIS and looks broken

Switch encoding to UTF-8 or Shift_JIS and re-load the file.

Q

I got zero duplicates

Check your key column choices and settings for empty keys or case sensitivity.