Remove Duplicate Lines
Paste a list and get every line exactly once — in its original order. Ignore case or surrounding spaces, keep the first or last copy, or switch to showing only the duplicates, only the unique lines, or a count of each.
How Duplicate Line Removal Works
Every line is compared with the lines before it; only the first copy is kept, so the list stays in its original order.
Lists collected from spreadsheets, logs, exports or copy-pasted pages often contain the same entry several times. This tool keeps the first occurrence of each line and drops the repeats — without sorting, so the order you had is the order you get.
Real-world lists are messy, so two options decide what counts as “the same”: Case sensitive (turn it off to treat Apple and apple as one) and Ignore spaces at ends, which matches lines that differ only by leading or trailing spaces or tabs. The line that is kept is output exactly as written.
Beyond cleaning, the modes answer common questions about a list: Only duplicates lists each value that appears more than once, Only unique lists values that appear exactly once, and Count shows how often each line occurs, most frequent first.
It uses a hash set, so the work grows linearly with the size of the list — 100,000 lines take a fraction of a second, and big files run in a background thread so the page never freezes.
Which Mode Do I Need?
Example input: apple, banana, apple, cherry, banana, apple (one per line).
Remove duplicates
Each line once, first copy kept: apple, banana, cherry. Tick Keep last occurrence to keep the last copy instead: cherry, banana, apple.
Only duplicates
Values that appear more than once, listed once each: apple, banana. Handy for finding repeated emails, IDs or SKUs.
Only unique
Values that appear exactly once: cherry. Every copy of a repeated value is left out.
Count
Occurrences per value, most frequent first: 3 apple, 2 banana, 1 cherry.
How to Use the Remove Duplicate Lines
Get your result in under ten seconds.
Paste your list
One item per line — or open/drop a text file. Blank lines and spaces are handled by the options.
Choose what counts as a duplicate
Toggle case sensitivity and whether surrounding spaces matter. The result updates as you type.
Copy or download
Copy the cleaned list, download it as .txt, or press “Use as input” to keep working on it.
Why Use the Remove Duplicate Lines on Developers Web Tools
Fast, accurate and private — built for developers.
Order preserved
No sorting — your list keeps its original order, first copies stay in place.
Flexible matching
Ignore letter case and stray spaces so near-identical lines are caught.
Four modes
Remove duplicates, list only the duplicates, list only unique lines, or count occurrences.
Built for big lists
Linear-time hashing; files over 256 KB are processed in a background thread.
Paragraph-friendly
Keep blank lines in place when de-duplicating structured text.
Private
Your text never leaves the browser — safe for customer lists and logs.
Frequently Asked Questions
No. Lines stay in their original order; only repeated copies are removed. If you want the result sorted, press Use as input and open the Sort Lines tool, or sort first and de-duplicate after.
The first one by default. Tick Keep last occurrence to keep the last copy instead — the kept lines are then ordered by where their last copy appeared.
Only when Case sensitive is off. Matching is Unicode-aware, so it works for accented and non-Latin text too. The kept line is output exactly as written, including its original case.
Lines that differ only by leading or trailing spaces or tabs are treated as the same. Spaces inside a line still matter, and the output keeps each line exactly as it was typed.
By default they are de-duplicated like any other line, so at most one blank line remains. Tick Keep blank lines to leave all of them in place. The Only duplicates, Only unique and Count modes always ignore blank lines.
Hundreds of thousands. Files up to 50 MB can be opened; anything over 256 KB is processed in a background worker so the page stays responsive, and very large results are previewed while Copy and Download include everything.
No. Everything runs locally in your browser.