Remove Duplicate Lines
Delete repeated lines, keep the first occurrence.
Duplicate lines creep into mailing lists, keyword lists, inventories and data exports.
How to use
- Paste your list, one item per line.
- Toggle case/whitespace options if needed.
- Click Remove duplicates, then copy the clean list.
About this tool
This tool keeps the first occurrence of each line and reports how many were removed.
Your list never leaves your browser.
How it works
The tool reads your text line by line and keeps a record of every line it has already seen. The first time a line appears it is kept; every later repeat is dropped. This runs in linear time with a hash set, so even lists with tens of thousands of lines process instantly.
Comparison is exact — "Apple" and "apple" count as different lines, and trailing spaces matter. If your data has inconsistent spacing, run it through the Whitespace Normalizer first for cleaner results.
Worked examples
Email list: A 5,000-address mailing list with 300 accidental duplicates becomes 4,700 unique addresses in one click.
Log cleanup: Strip repeated error lines from a server log so each unique error appears once.
Frequently asked questions
Does it keep the original order?
Yes — the first occurrence of each line stays in place; only later repeats are removed.
What does "ignore case" do?
"Apple" and "apple" count as the same line when enabled.
Is my list uploaded?
No — processing is 100% local.
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