Remove Duplicate Lines
Remove Duplicate Lines keeps the first occurrence of each line and drops later matches.
Example: remove duplicate lines
red red blue
red blue
How to use this tool
- Put one item per line.
- Choose whether to Ignore case, then run the deduplication.
- Check the first retained spelling and any whitespace differences.
How the result is made
The tool reads input as a line sequence and tracks previously seen values. It keeps the first copy, preserving the order of distinct lines. “red”, “red”, “blue” becomes “red”, “blue”. The Ignore case option compares lowercase line values, while the retained text still comes from the first occurrence.
When to use it
Use it to deduplicate a pasted list of names, URLs, or IDs before sorting or comparing it. Remove Consecutive Duplicate Words solves a different problem inside prose. Compare Two Lists shows overlap between separate lists without deleting anything.
Details to check
Whitespace counts in the comparison. “red” and “ red” are different unless you trim lines first; there is no ignore-spaces option. Blank lines can also be deduplicated, leaving at most one. Review case-sensitive identifiers before enabling Ignore case.
Questions people ask
Does it sort the result?
No. First-occurrence order is preserved.
Are red and Red duplicates?
Only when Ignore case is enabled.
Are leading spaces ignored?
No. Trim lines first if those should not matter.