Paste a list, click dedupe — keeps the first occurrence of each unique line in order.
Treats every line as an item and keeps only the first occurrence of each unique value. The defaults (trim whitespace) handle the most common case — accidental trailing spaces in a CSV column or copy-paste artefacts that prevent strict equality. Toggle case-insensitive for emails or usernames, sort if order doesn't matter, and remove empty lines to clean up at the same time.