Which duplicate is kept?

Always the first occurrence, in your original order. That makes the output predictable: dedupe a sorted-by-date CSV and the earliest row per key survives.

How do I dedupe a CSV by a specific column?

Switch to CSV mode, paste your file with its header row, then pick the key column — email, SKU, ID, anything. Rows repeating that value are dropped while all other columns stay untouched.

Is my data uploaded anywhere?

No. Parsing and deduplication run entirely in your browser with JavaScript. Nothing is sent to a server, which makes it safe for customer lists and other sensitive exports.

How big a list can it handle?

Hundreds of thousands of lines work comfortably; the practical limit is your browser's memory and paste buffer. For very large CSVs, use the download button instead of copy.

List & CSV Deduplicator

Remove duplicate entries from lists and CSV files by column — order-preserving, entirely in your browser

Input type

List (one entry per line)

Options

Trim whitespace around entriesCase-insensitive comparisonSkip empty lines

Duplicate handling

Summary

6 entries → 4 unique (2 duplicates removed)

Output

apple
banana
cherry
Cherry

Removed duplicates

apple×2
banana×2

List & CSV Deduplicator

Options

Summary

Output

Removed duplicates

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CSV Data Viewer

CSV to Chart

CSV to JSON Converter

CSV to Markdown Converter

Options

Summary

Output

Removed duplicates

Related guides

Fancy Fonts Are Just Unicode: How Social Bios Get Styled

Related tools

Base64 Toolbox

C# to VB.NET Converter

CSV Data Viewer

CSV to Chart

CSV to JSON Converter

CSV to Markdown Converter