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Bethemesh
Data & spreadsheets

CSV Deduplicator

Detect duplicate rows in a CSV using one or more selected columns, keep the useful records, and download a cleaned file.

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  • 100% local
  • Instant
  • Free
  • No account
  • Works offline
  • Clipboard

Leave empty to compare every column

Why use this tool?

Remove duplicate CSV rows using all columns or a custom key while choosing which occurrence should be preserved.

100% local and secure

Your data stays on your device and is never sent to our servers.

Smart processing

Clean, structure, and transform your data with rules tailored to the format being processed.

Supported formats

CSV, XLSX, and other tabular formats depending on each tool’s capabilities.

Save time

Get a clean, ready-to-use result in seconds without installing software or configuring a complex workflow.

Fonctionnement

How does this tool work?

The tool builds a comparison key for every row from the selected columns. It can normalize case and surrounding spaces, then keeps the first or last occurrence of each key before serializing a clean CSV with the original delimiter. The original row order is preserved whenever possible, making the cleaned file easier to review and reuse. Afterwards, it is ready for immediate import.

Use cases

Clean a contact list

Remove duplicates by email address, phone number, or a combination of fields.

Consolidate exports

Eliminate repeated rows after combining several source files.

Prepare an import

Reduce collisions and duplicate records before sending data to another system.

Guide

How to use this tool

  1. 1

    Add the data

    Paste the CSV or provide the information required by the tool.

  2. 2

    Configure processing

    Choose the columns, rules, or options that match your objective.

  3. 3

    Review the result

    Check the report, then copy or download the generated data.

Tips and best practices

  • Keep a copy of the source file before applying an important transformation.
  • Check the delimiter and header-row setting before running the operation.
  • All processing stays in your browser and no CSV file is uploaded.

Frequently asked questions

Are my CSV data uploaded?

No. Parsing, comparisons, and transformations are executed locally in your browser.

Are quoted fields supported?

Yes. The CSV engine supports delimiters inside quoted fields and multiline quoted content.

Can I download the result?

Yes. When a new CSV is produced, it can be copied or downloaded directly from the page.

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