What counts as a duplicate
Two lines are duplicates when they match exactly. Turn on “Ignore capital letters” to treat “Apple” and “apple” as the same line, and “Trim spaces” so a stray space at the start or end doesn't make a line look unique.
Empty lines are kept by default. Turn on “Remove empty lines” to drop them too.
Common uses
Cleaning email lists before an import, removing repeated keywords from a spreadsheet column, or de-duplicating log lines. Paste straight from Excel or Google Sheets — each cell in a column becomes one line.