Remove Duplicate Lines
Instantly remove duplicate lines from your text. Case-sensitive or insensitive, with whitespace trimming and order preservation. Free and private.
Free Online Duplicate Line Remover
Need to clean up a list of items, email addresses, URLs, or any other text with repeated lines? SmarterSources' Remove Duplicate Lines tool instantly identifies and eliminates duplicate entries from your text. Whether you are cleaning up data exports, deduplicating mailing lists, or filtering log files, this tool handles it all. Everything runs 100% in your browser — your text is never sent to any server.
How It Works
Paste your text into the input area, configure your options, and click "Remove Duplicates." The tool scans each line and keeps only the first occurrence of each unique line. You can choose whether the comparison is case-sensitive (so "Apple" and "apple" are treated as different lines) or case-insensitive (so they are treated as the same). Whitespace trimming removes leading and trailing spaces before comparison, preventing invisible differences from creating false duplicates.
Options Explained
Case Sensitive — When enabled, "Hello" and "hello" are treated as different lines. Disable this to treat them as duplicates regardless of capitalization. Trim Whitespace — Removes leading and trailing spaces from each line before comparing. This catches lines that look identical but have hidden spaces. Preserve Original Order — Keeps the unique lines in the order they first appeared. When disabled, lines may be reordered.
Common Use Cases
Data analysts use this tool to clean up CSV columns exported with duplicate values. Marketers deduplicate email lists before sending campaigns. Developers clean up log files and configuration lists. Teachers use it to create unique word lists from student submissions. The tool works with any text where you need to find and remove repeated lines quickly.
Frequently Asked Questions
How does the duplicate detection work?
The tool compares each line against all previously seen lines. When it encounters a line it has already seen, it removes the duplicate and keeps only the first occurrence. The comparison respects your case sensitivity and whitespace trimming settings.
What is the difference between case-sensitive and case-insensitive mode?
In case-sensitive mode, "Apple" and "apple" are considered different lines and both will be kept. In case-insensitive mode, they are treated as the same line, and only the first occurrence is kept. Use case-insensitive mode when capitalization does not matter for your data.
Does trimming whitespace modify my output text?
Yes. When "Trim Whitespace" is enabled, each line in the output will have its leading and trailing spaces removed. This ensures clean, consistent results. If you need to preserve exact spacing, disable this option.
Can I process very large files?
Yes. Since all processing happens in your browser, the tool can handle thousands of lines without any issues. There are no server limits or character restrictions. Performance depends on your device, but most computers handle tens of thousands of lines instantly.
Is my text stored or sent anywhere?
No. All text processing happens entirely in your browser using JavaScript. Your text never leaves your device. SmarterSources does not collect, store, or transmit any of the text you enter into this tool.
Does the tool handle empty lines?
Yes. Empty lines are treated like any other line. If your text has multiple empty lines, only the first one will be kept and the rest will be removed as duplicates. If you want to remove all empty lines entirely, you can combine this tool with the Sort Text Lines tool which has a "Remove Empty Lines" option.