Duplicate Lines Remover
Clean your text by removing duplicate lines while preserving original order
Data Disclaimer: This tool processes text locally in your browser. For sensitive data, we recommend verifying no information is sent to servers by checking your network traffic.
Tip: Paste your text (one item per line) to quickly find and remove duplicates. Works great for lists, logs, and datasets.
Advanced Options
Cleaned Text
Common Uses for Duplicate Line Removal
Data Processing
- Clean CSV or TSV data files
- Prepare datasets for analysis
- Remove duplicate entries from mailing lists
- Process server logs to find unique events
Code & Configuration
- Clean duplicate entries in configuration files
- Remove repeated imports in source code
- Process .env files with duplicate variables
- Clean up CSS with duplicate rules
"Our users report removing an average of 30-40% duplicate lines from typical text files, significantly reducing file sizes and improving data quality."
How Duplicate Line Removal Works
Line-by-Line Processing
The tool processes each line sequentially, comparing it against previously seen lines. By default, it preserves the first occurrence of each unique line and removes subsequent duplicates, maintaining your original order.
Comparison Methods
You can choose between case-sensitive or case-insensitive comparison. The tool can also either ignore or consider whitespace (spaces, tabs) at the start/end of lines when determining duplicates.
Performance Handling
The tool efficiently handles large texts (up to 100,000 lines) using optimized JavaScript algorithms. Processing happens entirely in your browser for privacy and speed.
Pro Tip: For very large files (10,000+ lines), consider processing in chunks for better performance. Use the "Keep empty lines" option when working with formatted text where blank lines have structural importance.
Frequently Asked Questions
Does this tool modify my original text in any way besides removing duplicates?
By default, the tool only removes duplicate lines while preserving all other content including whitespace and special characters. You can control this behavior with options like "Trim whitespace" and "Keep empty lines" in the advanced settings.
How does the tool determine what counts as a duplicate line?
The tool compares entire lines by default. Two lines are considered duplicates if they are exactly the same (optionally ignoring case and/or surrounding whitespace based on your settings). Partial matches (like similar sentences) are not considered duplicates.
Can I see which lines were removed or how many times duplicates appeared?
Yes! Enable the "Show duplicate counts" option in advanced settings to add [xN] markers after each line indicating how many times it appeared in the original text. For a full duplicate report, you might need to compare before/after versions manually.
Is there a limit to how much text I can process at once?
The tool can handle very large texts (up to 10MB or ~100,000 lines) in modern browsers. Performance may vary based on your device's memory. For extremely large files, consider splitting them into smaller chunks.
Does the tool work with tabular data or CSV files?
Yes, but for CSV files you'll want to ensure all lines (including headers) are properly formatted. The tool treats each line as a separate entry, so duplicate rows will be removed. For advanced CSV processing, consider a dedicated CSV editor.