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Duplicate Line Remover

Free online duplicate line remover. Paste any list and remove duplicate lines instantly. Case-insensitive or case-sensitive, keep first or last occurrence, or highlight duplicates instead. No signup required.

Keep:
Output:
0Input lines
0Unique
0Removed
0Output
Input
Deduplicated

Options

How to remove duplicate lines

  1. Paste your list into the input box on the left — one item per line. Duplicates are removed instantly.
  2. Choose Keep mode — First (default) keeps the first occurrence; Last keeps the final one. Useful when your list is ordered by recency.
  3. Choose Output mode — Unique shows the clean deduplicated list; Dupes only shows which lines were repeated; Mark dupes keeps everything but flags each repeated occurrence.
  4. Adjust options — toggle case-sensitivity, whitespace trimming, and empty line removal as needed.
  5. Copy the output with the copy button at the top right of the output panel.

Output modes explained

Unique

Default

Returns only lines that are not duplicated, plus one instance of each duplicated line. This is the standard deduplication mode — the output is a clean list with no repeats.

Duplicates only

Audit mode

Returns only the lines that appeared more than once, one instance each. Use this to audit what was duplicated — for example, to find common items across two merged lists, or to spot data entry errors.

Mark duplicates

Review mode

Returns all lines with duplicate occurrences marked as "← duplicate #N". Use this when you want to review duplicates in context before deciding which ones to delete manually — useful for data quality reviews.

Common uses for duplicate removal

Email list cleanup

Remove duplicate email addresses from a mailing list before sending a campaign to avoid double-messaging.

Keyword list deduplication

SEO keyword lists often accumulate duplicates across exports from different tools. Clean them before importing.

Merging two lists

After combining two data exports, use this tool to remove the overlap and get a clean union of unique entries.

Code import cleanup

Remove duplicate import statements or CSS class names that crept in during a merge or refactor.

Survey response audit

Find duplicate entries in form responses — same person submitting twice, or data pipeline errors.

Tag normalisation

Deduplicate tag, label, or category lists that grew organically with inconsistent capitalisation.

Frequently Asked Questions

How do I remove duplicate lines from a list?

Paste your list into the input box — one item per line. Duplicates are removed instantly and the clean list appears in the output. Use the copy button to grab the result.

Is the duplicate check case-sensitive?

No — by default "Apple" and "apple" are treated as the same line and one will be removed. Enable the Case-sensitive toggle if you want "Apple" and "apple" to be treated as distinct entries.

Can I keep the last occurrence instead of the first?

Yes. Use the Keep toggle to switch between First (default) and Last. Keep Last is useful when your list is ordered by date or priority and you want to retain the most recent entry for each unique value.

What does "Show duplicates only" do?

Instead of showing the deduplicated list, it shows only the lines that were duplicated — one instance each. Useful for auditing what was removed, or for finding common items across a large list.

What does "Mark duplicates" do?

Keeps all lines but appends a "← duplicate #N" marker to each repeated occurrence. Useful when you want to review duplicates in context before deciding which to delete manually.

Does it handle large lists?

Yes. Processing runs entirely in your browser with no server round-trips, so it handles thousands of lines without delay. There is no enforced limit on list size.

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