Last updated 28 August 2026
Three different questions about the same list
Removing duplicates is the obvious use, but it is not always the interesting one. Keeping only the lines that appeared more than once turns the same list into a report of what repeated — useful for finding double-entered records, overlapping email lists or recurring log entries. Keeping only the lines that appeared exactly once does the opposite, isolating the entries that are unique to the set. All three run off the same count, which is why they sit together here rather than as separate tools. Order is preserved by default because the position of the first occurrence usually carries meaning; sorting is available when it does not.
Common questions
Does it keep the first or the last occurrence?
The first. Later copies are dropped, which preserves the original order of the list. If you would rather have the result ordered alphabetically, tick the sort option instead.
What does ignoring case do to the output?
It treats “Apple” and “apple” as the same line for the purpose of counting, and keeps whichever version appeared first. The kept line retains its original capitalisation rather than being lowercased.
What is the difference between the three modes?
The first keeps one copy of everything. The second keeps only lines that appeared at least twice, which turns the tool into a duplicate finder. The third keeps only lines that appeared exactly once, isolating the entries that are unique.
Is my list uploaded anywhere?
No. Everything is processed in your browser and nothing is sent to a server, so it is safe for customer lists, emails or anything else you would not paste into an unknown site.