Remove duplicate lines

How two lines are judged to be the same

Two lines are considered duplicates when their text is identical, character for character. From each group of repeated lines, the first one is kept in its original position and the rest are removed.

The options only change the comparison, not the text that's kept:

• Ignore case: “London”, “LONDON” and “london” count as the same line. Accents still matter: “café” and “cafe” are different.
• Ignore leading and trailing spaces: “hello” and “ hello ” count as the same. The first one is kept exactly as written.
• Remove empty lines: deletes blank lines or lines containing only spaces. If you leave this unticked, empty lines stay where they are and aren't treated as duplicates, so the spacing between blocks isn't changed.

Sorting the result

With “Sort alphabetically”, the resulting list is sorted from A to Z using your language's alphabetical order: accented letters sort next to their unaccented versions, and numbers inside the text are sorted by value, so “item 2” comes before “item 10”.

If you don't tick this option, the original order is kept, which is useful when position matters, as in a priority list or a log.

Windows, Mac and Linux line breaks

Text copied from Windows uses two characters for each line break (CR and LF), while Linux and macOS use one (LF). The tool normalizes them before comparing, so two identical lines are detected as duplicates even if they come from different systems. The result uses LF line breaks, which any modern editor opens without trouble.