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// Text

Remove Duplicate Lines online

Remove duplicate lines from any text — case-sensitive or insensitive

Remove Duplicate Lines logo
by
CHUNKY
MUNSTER
// Input
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Input lines
0
Unique lines
0
Removed
// Output
Output will appear here...

How to Use the Remove Duplicate Lines

  1. Paste your list — one item per line — into the input field.
  2. Pick the comparison options: case-insensitive, trim whitespace, drop blanks, sort after.
  3. Click Remove Duplicates and read the input/unique/removed counters.
  4. Copy the unique list or download it as a .txt file.

Removing duplicates from a long list sounds trivial until you have to choose what counts as "duplicate". This tool gives you the three switches that actually matter: trim whitespace, ignore case, and ignore blank lines. The first occurrence of each line is always kept so the original order is preserved unless you explicitly opt into sorting.

How the Remove Duplicate Lines Works

Internally the deduper builds a Set keyed by the comparison form of each line (lower-cased and/or trimmed) but writes out the line in its original form. That keeps email addresses, file paths and IDs readable in the output even when you're comparing them case-insensitively.

Frequently Asked Questions

Is the original line order preserved?

Yes by default — the first occurrence of each line wins and later duplicates are dropped, leaving the rest of the list in its original order. Tick "Sort after dedup" if you want an A→Z order instead.

How are leading and trailing spaces handled?

With "Trim whitespace" enabled (default), " hello" and "hello " count as the same line. Disable trimming if your data is whitespace-significant — for example, indented config or YAML.

Does case-insensitive matching work for non-ASCII letters?

Yes. Comparison uses JavaScript's String.toLowerCase, which handles most Latin, Greek, Cyrillic and Cherokee letters. Edge cases like Turkish dotted/dotless I follow JavaScript's default Unicode rules, not locale-aware rules.

What's the practical input limit?

The whole input is held in memory as a Set of strings, so a few hundred thousand lines is comfortable on a modern laptop. Past a million lines you may notice the browser tab slow down — at that point a streaming command-line tool is faster.

Explore the full suite of Text tools and 290+ other free utilities at Chunky Munster.