Duplicate Line Remover

The Duplicate Line Remover takes a block of text and removes repeated lines while keeping the lines that remain in their original order. Paste a list, choose how duplicates should be handled, and copy a clean result. It is built for lists where order carries meaning, such as log lines, exported records, keyword sets, or email addresses, where sorting would scramble the sequence you need.

To see this online duplicate line remover work, click Load sample to paste nine lines: apple, Banana, cherry, apple, date, banana, cherry, apple and fig. Leave Keep unique and Keep first selected and tick Ignore case. The output is five lines, apple, Banana, cherry, date and fig, and the heading reads Output (5 lines, 4 removed). Banana keeps its capital because it appeared before banana. Switch to Keep only duplicates and the duplicate line remover returns apple, Banana and cherry instead.

The tool offers three modes because "remove duplicates" means different things depending on the task. The default mode keeps one copy of each line and drops the rest, which is the usual "make this list unique" operation. A second mode removes every line that has any duplicate at all, leaving only the lines that were already unique. A third mode does the opposite and returns just the lines that were duplicated, so you can see exactly what appeared more than once.

Comparison is exact by default, so two lines that differ only in capitalisation or trailing spaces count as different lines. Turn on the ignore-case option to treat "Apple" and "apple" as the same entry, and turn on Trim whitespace to strip leading and trailing spaces before comparing, which catches duplicates that were pasted with stray indentation. Trimmed lines are also trimmed in the output. You can also drop blank lines in the same pass so the output is exactly what you want.

Everything runs in your browser with JavaScript. Nothing is uploaded, there is no account, and the tool keeps working offline once the page has loaded, so it is safe for sensitive data that should never leave your machine. Because the work happens in memory, large lists of tens of thousands of lines process instantly, bounded only by the browser tab rather than an upload limit or a server round trip. The panel headings show how many lines went in, how many came out and how many were removed, so you can confirm the cleanup did what you expected before copying it out.