What counts as a duplicate line?

Two lines are considered duplicates when they match exactly after optional case normalization. Leading and trailing whitespace is preserved as-is; only the characters within the line are compared.

What does case-insensitive matching do?

With case-insensitive matching, "Apple", "apple", and "APPLE" are all treated as the same line. The original casing of the kept occurrence is preserved in the output.

What is the difference between keeping first and keeping last?

Keep First retains the earliest occurrence of each line and discards later repeats. Keep Last retains the final occurrence and discards the earlier ones. Use Keep Last when the most recent entry in a merged list is the most up to date.

Are blank lines treated as duplicates?

Yes. If your text has multiple consecutive blank lines, all but one will be removed when blank lines match each other. If you want to strip blank lines entirely, remove the blank line from the result manually.

Is there a size limit?

The tool runs entirely in your browser using JavaScript. It handles hundreds of thousands of lines without any server upload, so your data stays private. Practical limits depend only on your browser's available memory.

Does the tool change line endings?

The output uses the same line endings detected in the input (LF on most systems). No normalization is applied beyond deduplication.

Remove Duplicate Lines

Name: Remove Duplicate Lines
Availability: InStock
Author: Nham Vu

Paste text and instantly remove all duplicate lines, with control over case sensitivity and which occurrence to keep.

Input Text

0 lines

Options

Case Matching

Case-insensitive Case-sensitive

Keep Occurrence

Keep first Keep last

Result

Paste text and click "Remove Duplicates" to see the result here.

Copied!

Summary

Paste text and instantly remove all duplicate lines, with control over case sensitivity and which occurrence to keep.

How it works

Paste or type your text into the input box.
Choose case-sensitive or case-insensitive matching.
Choose whether to keep the first or last occurrence of each duplicate.
Click "Remove Duplicates" to process the text.
Review the statistics (original lines, duplicates removed, unique lines kept).
Click "Copy Result" to copy the deduplicated text to your clipboard.

Use cases

Clean up lists of URLs, emails, or names that have been merged from multiple sources.
Deduplicate log file entries before analysis.
Remove repeated lines from CSV exports or data dumps.
Tidy up keyword or tag lists with accidental repetition.
Prepare unique word lists for vocabulary or frequency analysis.
Merge two lists and remove overlap in seconds.

Frequently Asked Questions

Last updated: 2026-06-09 · Reviewed by Nham Vu