Question 1

Is the comparison case-sensitive by default?

Accepted Answer

Yes — 'Apple' and 'apple' stay as two separate lines unless you flip the case-insensitive toggle. That's the safer default, since for things like email addresses it's usually what you want, and you can always loosen it when you don't.

Question 2

Does it trim whitespace before comparing?

Accepted Answer

Optionally. With the trim option on, ' apple' (with a leading space) matches 'apple'. Without it, they're different lines. Turn it on when you're deduping a messy paste; leave it off if spacing matters to you.

Question 3

Does it preserve the original order?

Accepted Answer

Yes. Keeping first occurrence preserves the order you see in your input; keeping last preserves the order of last-seen items. Neither mode sorts — if you want sorting, run the sort tool after.

Question 4

What about blank lines?

Accepted Answer

Blank lines are treated the same as any other — multiple blanks get collapsed down to one. If you'd rather strip all blank lines entirely, the whitespace tool does that.

Question 5

Is there a size limit?

Accepted Answer

Thousands of lines are fine. Since it runs in your browser, truly huge files (hundreds of thousands of lines) can start to feel slow, depending on your device. For log files in that range, a command-line `sort -u` is faster.

Remove Duplicate Lines

What is Remove Duplicate Lines?

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