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Paste a list and get it back with duplicates removed. Order is preserved — the first occurrence of each line stays exactly where it was, rather than the list being silently sorted as a side effect, which is what most deduplicators do and is rarely what you want.
Comparison ignores case and surrounding whitespace by default, since that's usually what makes two entries the same in practice. The line you get back is exactly as you typed it, though: the normalisation is used for matching only, never to rewrite your data. There's also an inverted mode that shows only the lines which appeared more than once, for finding the duplicates rather than removing them.
Frequently asked questions
Does this change the order of my list?
No. The first occurrence of each unique line stays in its original position and later repeats are removed. If you also want it sorted, run the result through the sort lines tool afterwards.
Are 'Alice' and 'alice' treated as duplicates?
By default yes, and the same goes for lines that differ only by leading or trailing spaces. Both behaviours are toggles, so switch case sensitivity on when the distinction genuinely matters — like deduplicating codes or passwords.
How do I find duplicates rather than remove them?
Turn on "Show only the duplicates" and you'll get one copy of each line that appeared more than once — useful for auditing a list before you clean it, or for spotting double-entered records.
Is there a size limit?
Only your device's memory. Deduplication runs in a single pass using a hash set, so lists of hundreds of thousands of lines are fine, and nothing is uploaded — worth knowing when the list is customer emails.