How to remove duplicate lines from a list
- Paste the list, one entry per line.
- Decide whether Ram and ram are the same entry, and whether a stray space at the end counts.
- Press Remove the repeats.
- Check how many were dropped, then copy the cleaned list out or save it as a .txt.
Two lines that look the same and are not
This is the whole difficulty. A trailing space, one capital letter, or the same word typed two different ways keeps a repeat alive through most tools. An accented word built from a plain letter plus a floating accent, and the same word built from a single accented letter, are different sequences that draw identically on screen — and a phone keyboard and a desktop paste will happily produce one of each in the same column.
So the comparison runs on a tidied copy of each line: the two spellings are folded together first, then trimming and case-folding on top if you asked for them. What comes back out is your original line, character for character. Only the comparison ever sees the tidied version, because silently rewriting your text would be the worst bug this page could have.
Which copy survives, and in what order
By default the first occurrence stays where it was and everything after it goes. Ask it to keep the last one instead and the final version is written into the first one's position, so the order you were reading is the order you get back. That is the setting you want when a list has been appended to and the later entry is the corrected one.
Sorting is optional and starts off. Turned on, numbers sort the way a person expects: item 2 before item 10 rather than after it. You can also invert the whole job and ask for only the lines that appeared more than once, which is how you find out what was duplicated instead of quietly removing it.
What it will not catch
It compares whole lines and nothing smaller. Two rows describing the same person with a different phone number are two different lines, and both survive. A typo is a different line too. There is no fuzzy matching here and there deliberately is not, because a tool that decides two nearly-identical entries are the same one will eventually delete a real record.