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CSV Duplicate Checker

Paste a CSV and instantly find duplicate rows or duplicates based on specific columns. Everything runs in your browser (no upload).

Output a quick report, a de-duplicated CSV, or a duplicate-only CSV for review.

Category: Data · URL: /tools/csv-duplicate-checker.html
Auto picks the delimiter from the first non-empty line.
Used only when Delimiter = Custom.
If Compare full row is off, duplicates are detected by these columns (names require header).
0 = don’t list keys (counts still shown).
Tip: For column-based matching, uncheck Compare full row and enter key columns.
Related tools: CSV Formatter · Online CSV Generator · JSON Pretty Print · XML Pretty Print · SQL Checker (Client‑Side)
Privacy: runs locally in your browser. No uploads, no tracking scripts.

How to use

Use this tool to detect duplicates by full row or by selected key columns.

  1. Paste your CSV into the input box.
  2. Pick a delimiter (or keep Auto), and set whether the first row is a header.
  3. Choose Compare full row or enter key columns (names or 1-based indexes like 1,3).
  4. Click Check duplicates.
  5. Switch Output mode to get a unique CSV or a duplicate-only CSV.
Keywords this page targets (natural cluster): csv duplicate checker, find duplicates in csv, csv duplicate rows, csv duplicate values in column, remove duplicates from csv, deduplicate csv online, csv unique rows generator, csv duplicate detector, find duplicate emails in csv, csv duplicates by multiple columns, csv duplicates with header row, case insensitive csv duplicate check, trim spaces csv duplicates, csv duplicate checker client side, csv duplicate check without upload, duplicate-only csv export, unique-only csv export, check duplicates in tab delimited file, find duplicates in semicolon csv
Secondary intents covered: Find duplicate rows in a pasted CSV, Detect duplicates using one or more key columns, Create a unique-rows CSV to copy into another tool, Export only duplicate rows for auditing, Handle quoted fields and different delimiters (comma, tab, semicolon, pipe), Run a duplicate check locally without uploading sensitive data, Get counts for duplicate groups and total duplicate occurrences, Compare case-insensitively and/or with trimmed whitespace

FAQ

Does this CSV duplicate checker upload my file?

No. It runs client-side in your browser; the CSV stays on your device.

Can I detect duplicates by a specific column (like email)?

Yes—turn off Compare full row and enter key columns by name (with header) or by 1-based index (e.g. 1,3).

What counts as a duplicate row?

Rows are duplicates when their comparison key matches (full row or selected columns), after applying trim/case options.

Does it handle quoted CSV fields and commas inside quotes?

Yes. Quoted fields and escaped quotes ("") are parsed correctly.

How do I remove duplicates and keep only unique rows?

Set Output mode to Unique CSV (or Report + Unique CSV) and choose whether to keep the first or last occurrence.

How do I export only the duplicates?

Use Duplicate-only CSV output and choose whether to include the first occurrence in the duplicate export.

Why does Auto delimiter pick the wrong separator?

Auto uses the first non-empty line; if your header is unusual, set the delimiter explicitly (comma/tab/semicolon/pipe/custom).