Remove Duplicate Lines
Find and delete duplicate lines from a list, with a report of exactly which lines repeated and how many times.
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Duplicate lines
How to use this tool
- Paste a list into the box, one item per line.
- Turn on 'Ignore case' if 'Apple' and 'apple' should count as the same line, and 'Trim whitespace' if leading or trailing spaces should be ignored when comparing.
- Choose whether to keep the first or the last occurrence of each repeated line.
- Check the 'Duplicates found' list to see exactly which lines repeated and how many times, before you commit to any change.
- Click 'Remove Duplicates' to delete the repeats, or 'Copy Result' to copy the cleaned list without changing the box.
About this tool
Most duplicate line removers give you a cleaned list and nothing else, so you cannot tell what was actually removed or why two lines that looked identical were not treated as duplicates. This tool shows its working: every line that repeats is listed with its exact repeat count before anything is deleted, so you can see whether "New York" and "new york " were merged because of the case and whitespace settings, or kept apart because they were not. Comparison is configurable rather than fixed. Turn on 'Ignore case' to merge lines that only differ in capitalisation, and 'Trim whitespace' to merge lines that only differ in leading or trailing spaces, which is the single most common reason a spreadsheet export looks like it has no duplicates when it does. Choosing to keep the first or the last occurrence controls which version of a repeated line survives when the two are not byte-identical. It is built for cleaning email lists, keyword lists, CSV columns pasted as text, log output, and any list where the same entry can appear more than once by accident. Everything runs locally in your browser using JavaScript: your list is never uploaded, stored, or seen by a server, which makes it safe for customer data, internal lists, or anything confidential.
Frequently asked questions
How do I remove duplicate lines from a list?
Paste the list into the box. The tool immediately reports how many lines are duplicates and lists each repeated line with its count. Click 'Remove Duplicates' to delete the repeats, keeping either the first or the last occurrence of each line depending on the toggle you chose.
What is the difference between 'Ignore case' and 'Trim whitespace'?
'Ignore case' treats 'Apple' and 'apple' as the same line. 'Trim whitespace' treats 'Apple' and 'Apple ' (with a trailing space) as the same line. Both are off by default for exact matching and can be combined, which is usually the right setting for a messy export.
Does it keep the first or the last copy of a repeated line?
Whichever you choose. 'Keep first occurrence' preserves the original order and drops later repeats. 'Keep last occurrence' is useful when a later row in an export is the corrected or more recent version of an earlier duplicate.
Can I see which lines were duplicated before deleting anything?
Yes. The 'Duplicates found' section lists every line that appears more than once, with its exact repeat count, updated live as you type or paste. Nothing is deleted until you click 'Remove Duplicates'.
Is there a limit on how much text I can paste?
No fixed limit. Processing happens locally in your browser rather than on a server, so the only practical constraint is your device's memory. Lists of tens of thousands of lines handle comfortably.
Is my list uploaded anywhere?
No. The whole comparison and cleanup runs in JavaScript on your device. Nothing is transmitted, logged, or stored, and closing the tab discards it completely.