Remove Duplicate Lines
Remove duplicate lines and keep only unique entries, in original order. Optional case-insensitive matching and whitespace trimming. Browser-based.
settingsOptions
What is the Remove Duplicate Lines?
A duplicate line remover walks through your text, keeps the first time each line appears, and drops every subsequent copy. Useful for cleaning up exports, mailing lists, log files, or any input where the same value got appended more than once and you want one of each.
How to use the Remove Duplicate Lines
- 1
Paste your text
Drop the source into the input pane. Each line counts as one item to compare against the others.
- 2
Toggle the comparison options
Case-insensitive treats "Foo" and "foo" as the same. Trim whitespace ignores leading and trailing spaces when comparing.
- 3
Read the deduped output
The output pane shows only unique lines, in the order they first appeared. The label tells you how many duplicates were removed.
- 4
Copy the result
Hit Copy to send the deduplicated text to your clipboard.
Frequently Asked Questions
How does duplicate detection work?
Each line gets compared against the lines that came before it. The first time a line appears, it's kept; every later occurrence is dropped. The comparison runs in a single pass using a Set, so the work scales linearly with input size.
Does it preserve line order?
Yes. The first occurrence of each unique line stays in its original position. So if your input is [apple, banana, apple, cherry], you get [apple, banana, cherry] in that exact order.
Can it handle large texts?
Yes. The dedup runs in your browser using a Set lookup, which is O(1) per line. Tens of thousands of lines deduplicate in milliseconds; hundreds of thousands work fine on a modern device.