Remove duplicate lines from any text, ignoring case and whitespace. Keep the first or last occurrence and see which lines repeated.
All processing happens in your browser. Your text never leaves your device.
Splitting your input into lines and comparing them is a classic set problem, and this tool solves it in one pass. Each line is read in order, normalized by the rules you choose, and looked up in a hash map that remembers whether it has been seen and how many times.
No. All processing happens in your browser using plain JavaScript. The text never leaves your device, and nothing is stored or transmitted after you leave the page.
When a line appears several times, the tool must decide which copy to keep. 'Keep first' preserves the first occurrence and drops the rest; 'Keep last' drops everything before the final occurrence and keeps that one. Both options preserve the original order of the surviving lines.
With 'ignore case' enabled, 'Apple' and 'apple' count as the same line. With 'ignore whitespace' enabled, leading and trailing spaces are ignored when comparing lines — 'hello ' and 'hello' match. The option that is checked determines how duplicates are detected; the kept lines are always the original text.
Yes. The tool compares lines, not words or substrings. A line counts as a duplicate only when it is identical to a previous (or later, with 'keep last') line after the case/whitespace rules you choose. Partial overlaps are left untouched.
As much as your browser comfortably handles — typical documents of tens of thousands of lines are instant. The repeated-lines list is capped at 50 entries to keep the page fast, but the full deduplicated result is always complete.
If you just finished with Duplicate Line Remover, the natural next steps are Text Whitespace Cleaner, Unique Word Counter, Text Case Converter, or browse every tool in Daily Tools.