Which duplicate is kept?

The first occurrence, preserving the original row order for everything that stays.

How do I dedupe a mailing list by email?

Type the column name (e.g. email) or its number into the “Dedupe by column” box — rows sharing that value are collapsed to one.

Is matching case-sensitive?

No — values are trimmed and lowercased before comparison, which is what you almost always want for emails and IDs.

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Remove Duplicate Rows from CSV

Delete duplicate rows from a CSV free in your browser — dedupe by whole row or a specific column like email. No upload.

100% free
Runs in your browser — nothing is uploaded
No signup required

First row is headersDedupe by column (name or #, blank = whole row)

Duplicate rows sneak into exports, mailing lists, and merged files constantly. This tool removes them in one click — either exact duplicate rows, or duplicates of a single key column such as email or order ID.

Column matching is case-insensitive and whitespace-trimmed, so “Ada@Example.com ” and “ada@example.com” count as the same. The first occurrence is always kept.

Example

Input

email
a@x.com
a@x.com
b@x.com

Output

email
a@x.com
b@x.com  (1 duplicate removed)

Your data never leaves your device

Like everything at OpenCSV, this tool processes files locally in your browser. There is no upload, no server-side processing, and no copy of your data anywhere — which makes it safe for customer lists, financial exports, and other sensitive files.

/ frequently asked

Frequently Asked Questions

The first occurrence, preserving the original row order for everything that stays.

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