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Duplicate Line Remover

Free online tool to remove duplicate lines from text and keep only unique lines.

🛠️ Options

📝 Input Text

📊 Statistics

Total Lines0
Unique Lines0
Removed Lines0

✨ Result (Unique Lines)

Remove duplicate lines. Use 'Case Sensitive' to distinguish character case, and 'Sort Result' to alphabetically order the output.

Key Features​

  • Remove Duplicate Lines: Automatically detect and remove identical lines
  • Case Sensitivity: Choose whether to distinguish case
  • Sort Option: Sort results alphabetically
  • Real-time Statistics: Display total lines, unique lines, and removed lines count
  • Preserve Order: Maintain original order while removing duplicates (when not sorting)

How to Use​

Basic Usage​

  1. Enter text in the input area (one per line)
  2. Duplicates are automatically removed and results are displayed
  3. Click the "Copy" button to copy results to clipboard

Option Settings​

  • Case Sensitive: When checked, treats "Apple" and "apple" as different
  • Sort Output: When checked, sorts results alphabetically

Use Cases​

1. Email List Cleanup​

Input:
user1@example.com
user2@example.com
user1@example.com
user3@example.com

Output:
user1@example.com
user2@example.com
user3@example.com

2. Keyword List Cleanup​

Useful for removing duplicate keywords in marketing or SEO work.

Input:
react
javascript
react
vue
javascript
angular

Output:
react
javascript
vue
angular

3. File Path Cleanup​

Use to remove duplicate paths from log files or scripts.

Input:
/home/user/docs
/home/user/downloads
/home/user/docs
/home/user/pictures

Output:
/home/user/docs
/home/user/downloads
/home/user/pictures

4. Data Cleanup​

Use to remove duplicate items from CSV files or databases.

Detailed Option Explanation​

Case Sensitive​

When Unchecked (default)​

Ignores case when determining duplicates.

Input:
Apple
APPLE
apple
Banana

Output:
Apple
Banana

When Checked​

Distinguishes case when determining duplicates.

Input:
Apple
APPLE
apple
Banana

Output:
Apple
APPLE
apple
Banana

Sort Output​

When Unchecked (default)​

Maintains original order (first occurrence order).

Input:
Zebra
Apple
Banana
Apple

Output:
Zebra
Apple
Banana

When Checked​

Sorts results alphabetically.

Input:
Zebra
Apple
Banana
Apple

Output:
Apple
Banana
Zebra

Statistics Information​

The tool displays three statistics in real-time:

  • Total Lines: Total number of input lines
  • Unique Lines: Number of lines remaining after removing duplicates
  • Removed Lines: Number of duplicate lines removed

Practical Tips​

1. Processing CSV Files​

When removing duplicates from a specific column of a CSV file:

  1. Copy the column from Excel or spreadsheet
  2. Paste into this tool
  3. Copy again after removing duplicates and paste back

2. Log Analysis​

Useful for finding unique IP addresses or users in server logs.

3. Code Cleanup​

Can be used to remove duplicates from import statements or dependency lists.

4. Large Data Processing​

Can quickly process thousands of lines.

Algorithm Explanation​

This tool uses JavaScript's Set data structure to efficiently remove duplicates:

const seen = new Set();
lines.forEach((line) => {
  const key = caseSensitive ? line : line.toLowerCase();
  if (!seen.has(key)) {
    seen.add(key);
    uniqueLines.push(line);
  }
});

Time complexity: O(n) - very efficient!

Frequently Asked Questions​

Q: How are blank lines handled?​

Blank lines are treated the same as regular lines. If there are multiple blank lines, only one remains.

Q: Do leading/trailing spaces affect duplicate detection?​

Yes. "Apple" and " Apple " (with leading space) are treated as different. To remove spaces, use the Whitespace Remover tool first.

Q: How many lines can be processed at maximum?​

Theoretically unlimited, but depends on browser memory. Generally, tens of thousands of lines can be processed without issues.

Q: How does the sort option work?​

Uses JavaScript's localeCompare for natural alphabetical sorting. Korean text is also sorted alphabetically.

Performance​

  • Processing Speed: Processes 10,000 lines in under 1 second
  • Memory Efficient: Optimized with Set data structure
  • Real-time Processing: Results display immediately upon input

Privacy Protection​

This tool operates completely client-side. Your input data is not transmitted to any server and is processed only in your browser.