Duplicate Line Remover
Remove duplicate lines from text instantly. Keeps first occurrence, preserves order.
A duplicate line remover strips repeated lines from text while keeping the first occurrence in its original position. Line order is preserved, which helps with log files, structured data, and email lists. Case sensitivity and blank-line removal are toggleable.
Paste text below to remove later repeats. The comparison is line-by-line, so whitespace and case settings can change what counts as a duplicate.
Good to know before removing duplicate lines
The tool compares each complete line. It does not parse CSV columns, trim hidden characters, or decide which duplicate row is more correct.
First line wins
When the same line appears three times, the first copy remains and later copies are removed.
Case can matter
With case sensitivity on, Admin and admin are different lines.
Whitespace can hide duplicates
A trailing tab or extra space makes a line different unless you clean whitespace first.
Blank-line removal is separate
Turn it on when empty rows are noise, and leave it off when blank lines separate sections.
When Duplicate Lines Become a Problem
Duplicate lines sneak into data more often than you'd expect. Log files repeat entries during retries. CSV exports contain duplicate rows from bad joins. Configuration files accumulate repeated entries over months of edits. Mailing lists end up with the same email address on multiple lines.
Manually scanning for duplicates is impractical beyond a few dozen lines. This tool processes thousands of lines instantly, keeping the first occurrence of each unique line while preserving the original order. Toggle case sensitivity for text data, or enable blank line removal for cleaner output.
All processing happens in your browser. Your data stays on your device, important when cleaning log files, customer lists, or database exports.
Processing Modes Compared
| Mode | What It Does | Best For |
|---|---|---|
| Case-sensitive | "Hello" and "hello" are different lines | Code, config files, case-significant data |
| Case-insensitive | "Hello" and "hello" are treated as the same | Email lists, names, general text |
| Remove blank lines | Strips empty lines from the output | Log cleanup, data formatting |
Common Use Cases
Cleaning email lists. Lists from multiple sources contain duplicates. Case-insensitive mode catches "john[at]example.com" and "John[at]example.com" as the same entry. Clean before importing to your email platform to avoid double-sending.
Deduplicating log entries. Application logs repeat the same error thousands of times. Deduplicating shows you the unique errors, making it easier to identify distinct issues without scrolling through repetitive output.
Cleaning config files. Hosts files, .gitignore rules, and environment variables accumulate duplicates over time. Removing them keeps configs clean and prevents unexpected behaviour from repeated entries.
Preparing import data. CSV and TSV files from database exports often contain duplicate rows from bad joins. Deduplicating before import prevents constraint violations and inflated record counts.
Deduplicating keyword lists. SEO keyword research generates lists with many repeats across tools and sources. Strip duplicates to get a clean set of unique terms for your content plan.
Before and After
Before (8 lines)
john[at]example.com sarah[at]example.com john[at]example.com mike[at]example.com sarah[at]example.com john[at]example.com anna[at]example.com mike[at]example.com
After (4 lines)
john[at]example.com sarah[at]example.com mike[at]example.com anna[at]example.com
Order preserved, first occurrence kept, duplicates gone. Half the list was duplicates, not unusual for merged data sources.
Worked Deduplication Example
Imagine a support team exports issue codes from two systems and pastes them into one list:
Input
ERR-042 ERR-105 ERR-042 err-105 ERR-200 ERR-105
Case-sensitive output
ERR-042 ERR-105 err-105 ERR-200
With case sensitivity on, ERR-105 and err-105 remain separate. Turn case sensitivity off if those should count as the same issue code.
Command-Line Alternatives
| Task | Command | Notes |
|---|---|---|
| Remove adjacent duplicates | sort file.txt | uniq | File must be sorted first |
| Remove all duplicates | awk '!seen[$0]++' file.txt | Preserves original order |
| Show only duplicated lines | sort file.txt | uniq -d | Useful for finding what's repeated |
| Count occurrences | sort file.txt | uniq -c | Prepends count to each line |
| Case-insensitive dedup | awk '!seen[tolower($0)]++' file.txt | Treats "Hello" and "hello" as same |
These commands work on Linux and macOS terminals. On Windows, use WSL or PowerShell's Get-Content file.txt | Sort-Object -Unique. For scripted jobs or very large files, command-line tools are easier to repeat and review.
Related Tools
How to use this tool
Paste your text with duplicate lines
Toggle case sensitivity and blank line options
Copy the deduplicated result
Common uses
- Deduplicating email lists before import
- Cleaning log files to show unique errors
- Removing duplicate entries from configuration files
- Preparing clean data for database imports
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Frequently Asked Questions
Does this tool preserve the original line order?
Is the comparison case-sensitive?
Can I remove blank lines too?
Is my data uploaded anywhere?
How many lines can this handle?
What's the difference between trim duplicates and sort + uniq?
Can I use this to deduplicate a CSV?
Does this handle Windows-style line endings?
Can I deduplicate by one field only?
Why might the output be shorter than I expected?
Results are for general informational purposes only and should be checked before use. They are not professional advice. See our Disclaimer and Terms of Service.