Remove duplicate rows from CSV — without uploading your file.

By default, every column value must match exactly — it's a full-row comparison. You can narrow this by ticking specific "key columns" (e.g. just email) to match on those only. Comparison is case-sensitive and whitespace-sensitive; use Find & Replace first if you need normalization.

Keep first: the first occurrence of a duplicate row stays, later copies are removed. Keep last: the latest occurrence wins, earlier copies are removed. "Keep last" is useful when your file is chronological and the most recent record is most accurate.

Likely one of: (1) hidden whitespace — "[email protected]" and " [email protected] " are different strings. (2) case differences — "[email protected]" and "[email protected]" are different. (3) invisible characters like BOM or non-breaking space. The tool is deliberately strict. Run Validate first to find these; use Find & Replace to normalize them.

Yes. Tick the checkbox for that column in "Key columns". Leave all others unticked. Rows with the same email will be deduped regardless of other column values.

Yes. Drop an Excel file and remove duplicates works identically. You can output back to XLSX if you need to preserve Excel formatting.

They're treated as equal in string comparison. The tool uses string-level comparison for row matching so mixed numeric/string exports still match duplicates correctly.

No. Hash-based duplicate detection scales linearly. Files with 5 million rows work in Chrome or Edge with enough RAM — the limit is your browser's memory, not the algorithm.

Not currently — the tool only shows the count. If you need the removed rows, use the Filter tool with a match rule to isolate duplicates before removing duplicates.

Not directly supported. Run Find & Replace first with Regex mode and your preferred normalization (e.g. lowercase the email column), then remove duplicates.

Yes — "💾 Save settings" stores your output format and keep-first/last preference. Column selections are per-file so they're not saved; re-tick them quickly on each visit.

Yes. As soon as you load a file, a preview table shows the first 10 unique rows with a live counter ("N duplicate rows would be removed — M unique rows remain"). The preview updates instantly when you tick/untick key columns or switch between keep-first and keep-last, so you always see the effect of your choices before hitting download.

Sort your file first by the date column (newest first) using the Sort CSV tool, then open this tool. Tick only the email column as the key column and choose Keep first occurrence. Because the newest row is now first, dedupe keeps the most recent record for each email. Works for Leads, Contacts, or any CRM export with timestamped rows.