Duplicate Line Finder groups the lines that appear more than once, showing each group's count and line numbers.
It can also return only the duplicates, only the lines that appear once, or the whole list with duplicates removed. It runs in your browser.
The first occurrence by default. There is an option to keep the last one instead.
Yes. Ignore inner whitespace treats runs of spaces and tabs as a single space when matching.
De-dupe keeps the surviving lines in their original order.
No. The tool runs entirely on this page.