Paste a list and every line that has appeared before is dropped. The copy that stays is the first one, written exactly as you typed it, and the order of what remains is the order you started with — nothing is sorted behind your back. By default two lines that differ only in capitalisation or in trailing spaces count as the same line, because that is almost always what a pasted list needs; both of those can be turned off.
This page loads no libraries at all — the work is done by the browser itself. Your file is read on your own machine and never sent anywhere — open your browser's network tab and watch while you use it.
The first one, exactly as you wrote it. Comparison happens on a normalised version of the line, but what gets written back is the original text. A tool that compares in lower case and then returns the lower-cased line has quietly edited your data, which is a strange thing for a deduplicator to do.
No. The lines that survive stay in the order they arrived. If you want them sorted as well, run the sort tool afterwards — keeping the two jobs separate means neither one surprises you.
By default yes, and so are "apple" and "apple " with trailing spaces. Both behaviours have a switch. Turn matching on for case when you are working with identifiers or code, where the difference is real.
The first blank line is kept and the rest are treated as duplicates, so a list padded with empty rows comes back with one separator instead of ten.
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