CSV Deduplicator

How to use

1. 1Paste or open a CSV in the source box. The delimiter is auto-detected, and the parsed row and column count appears below the input.
2. 2Choose the duplicate key: All columns for an exact row match, or Choose key columns to pick the fields that define a duplicate (for example, email or order_id).
3. 3Pick whether to keep the first or the last occurrence of each duplicate. Toggle Case sensitive, Trim whitespace, and Drop blank rows to match your data.
4. 4Read the stats panel: duplicates removed, duplicate groups, and blank rows dropped. Scan the duplicate groups list to audit what was collapsed.
5. 5Copy the deduplicated CSV with Copy CSV or grab a deduplicated.csv file with Download. Switch the output delimiter if you need a TSV or a pipe-separated file instead.

About this tool

CSV Deduplicator reads a CSV (or TSV, semicolon, or pipe-separated file) and emits a new file with duplicate rows removed. The duplicate key can be every column at once, which is the standard exact-row match, or a subset of columns such as email, order_id, or customer_id, which is the right policy when later columns carry rolling fields like updated_at or total_spend that should not block a match. The kept row can be the first occurrence (the typical default) or the last occurrence (useful when rows are sorted by time and the latest row carries the freshest values). Comparison can ignore casing and ignore surrounding whitespace, so ALICE@x.com, alice@x.com, and " alice@x.com " collapse into one row when those toggles are on. Blank rows can be dropped on the way in to keep the output clean. The header row, when present, is preserved at the top while only the data rows are deduplicated. The result panel reports the number of duplicate rows removed, the number of duplicate groups (two or more rows sharing the same key), and the number of blank rows dropped, and the top duplicate groups are listed with their occurrence count and the first source line so you can audit what was collapsed before downloading. Delimiters are auto-detected from the input across comma, tab, semicolon, and pipe, and the output delimiter can be different from the input delimiter so a TSV can be deduplicated and downloaded as a CSV. The parser follows RFC 4180, so quoted fields, embedded commas, embedded newlines, and escaped quotes round-trip correctly. Everything runs locally in your browser; the file you paste or open here is never uploaded to a server.

Free to use. Works in your browser. No signup, no login.