Clean up
Remove duplicate lines
Find repeats before you delete them, with control over whether case and whitespace count as a difference.
What counts as a duplicate
Deduplication is only well-defined once you decide what "the same" means, and the defaults matter more than the algorithm. Three questions decide the answer.
Does case matter? For email addresses, no — the local part is technically case-sensitive but effectively never treated that way, so Hello@example.com and hello@example.com are the same address. For passwords or IDs, case absolutely matters. Default here is case-insensitive.
Does surrounding whitespace matter? Almost never. A line with a trailing space is the same value as one without, and lists copied out of spreadsheets are full of them. Default is to trim before comparing.
Which copy survives? This tool keeps the first occurrence and preserves the original order of what remains, so your list is not silently re-sorted. If you want it sorted too, that is a separate action.
Inspect before you delete
The default behaviour of most dedupe tools is to hand back a shorter list and tell you nothing about what went missing. That is fine when you trust the input and risky when you do not — a stray leading space or an unexpected case difference can mean the tool removed something you needed, or kept something you thought was a duplicate.
The panel shows how many lines were removed, how many distinct values repeated, and which values repeated most, before you apply anything. "Keep only the duplicates" inverts the operation so you can look at exactly what is repeating — useful for auditing a mailing list or finding accidental copy-paste in a keyword set.
Common questions
Does it keep the first or the last copy?
The first, and the order of the remaining lines is preserved. Your list is not silently re-sorted. If you want it sorted as well, that is a separate action.
Are lines that differ only in case duplicates?
By default yes, which is usually right for email addresses and keywords. Switch on Case sensitive when case is meaningful, as it is for passwords, IDs and code.
Can I see the duplicates before removing them?
Yes. The panel lists how many lines repeat and which values repeat most as you type, and "Keep only the duplicates" inverts the operation so you can inspect exactly what is repeating.