Remove Duplicate Lines from a Text File — Online, Free

Updated: May 2026

You have a .txt file full of repeated lines and no desire to install a command-line utility or write a script. This guide shows you how to deduplicate any text file in seconds using only your browser.

Paste your file content and get a clean version instantly.

Open the tool →

Step-by-step: clean a text file in your browser

Open your .txt file in any text editor — Notepad (Windows), TextEdit (Mac), VS Code, or any other editor.
Select all the content with Ctrl+A (or Cmd+A on Mac), then copy with Ctrl+C.
Open the Flowfiles Remove Duplicate Lines tool and paste into the input field with Ctrl+V.
The output column updates immediately with duplicates removed. Adjust options if needed (case insensitive, trim whitespace, sort).
Click Download .txt to save the deduplicated file, or Copy to paste it back into your editor.

For very large files (millions of lines), modern browsers handle the processing in under a second thanks to native JavaScript Map performance.

When does a text file accumulate duplicates?

Duplicate lines in text files are more common than you might think, and they usually appear for one of these reasons:

Multiple log files merged into one, with repeated error messages or timestamps.
A keyword list assembled from several research exports (Ahrefs, Semrush, Google Search Console).
An email list built by combining several CSV exports, where the same contact appears multiple times.
A word list or dictionary file that has been modified over time and gained accidental copies.
A database export where a JOIN query produced repeated rows saved as plain text.
Configuration file entries accidentally duplicated by a deployment script.

Command-line alternatives for technical users

If you prefer not to use a web tool, here are the native commands to deduplicate a text file:

Linux / macOS: sort -u input.txt > output.txt — sorts and removes duplicates simultaneously.
Linux / macOS (preserve order): awk '!seen[$0]++' input.txt > output.txt
Windows PowerShell: Get-Content input.txt | Sort-Object -Unique | Set-Content output.txt
Python: open('out.txt','w').write('\n'.join(dict.fromkeys(open('in.txt').read().splitlines())))

The browser tool is faster for quick, one-off tasks. The command-line options are better for automation or very large files (several GB) that might exceed available browser memory.

Frequently asked questions

Can the tool open .txt files directly?

The tool uses a paste-based workflow. Open your file in a text editor, copy the content, and paste it. This approach avoids any file upload entirely.

What if my file has Windows line endings (CRLF)?

The tool normalizes both CRLF and LF line endings automatically. Files created on Windows are handled correctly.

Will the output preserve the original line order?

Yes, by default. The tool keeps the first occurrence of each line in its original position. Enable "Sort output" only if you want alphabetical ordering.