About this tool
Email lists, keyword exports, log files and spreadsheet columns often contain repeated lines. This tool removes them while keeping the first occurrence of each line in its original position.
You decide how strict the comparison is: case-sensitive or not, with or without leading and trailing spaces, and optionally ignoring blank lines. It shows the original and final line counts so you can see what changed.
How to use the Duplicate Lines Remover
- Paste your list into the text box, or press Load sample to try it.
- Choose matching options: case-sensitive, trim whitespace, remove empty lines and optional sorting.
- Press Remove duplicates.
- Check the counts, then copy the result or download it as a text file.
Practical examples
How it works
The tool splits text at line breaks (Windows, Mac and Unix styles), then reads each line once. A JavaScript Set records the comparison key of every line already seen. If the key is new, the line is kept; otherwise it is counted as a duplicate. This takes time proportional to the number of lines, so very large lists remain fast.
Case-insensitive matching compares lowercase versions, but the output keeps the first line exactly as typed.
Privacy and file processing
Your text is processed in your browser only. It is never uploaded or saved.
See our Privacy Policy for details on cookies, local storage and advertising.
Frequently asked questions
Is the first or last duplicate kept?
The first occurrence is kept and later ones are removed.
How large a text can I use?
Memory is the only limit. Lists of several hundred thousand lines work on modern devices, though phones may be slower.
Does it remove lines that are only similar?
No, only lines identical under your chosen options.
Is my text uploaded?
No. Everything runs in the page; there is no server involved.
Related tools
Results are for general information. Check important figures against official sources. Read the disclaimer.