1
Comparison keys are separate from output text
Whitespace trimming and lowercase conversion are applied to a temporary key. The first original line is retained exactly, so normalization does not silently rewrite its visible content.
Remove Duplicate Lines
Paste text and instantly remove duplicate lines while preserving order.
How to Use Remove Duplicate Lines
- 1
Paste your text
Enter the text containing duplicate lines to clean.
- 2
Remove duplicates
Click to remove all duplicate lines, keeping the first occurrence.
- 3
Copy clean text
Click copy to grab the deduplicated text output.
Tested tool guide
Text and writing tools
Checked July 30, 2026
What Remove Duplicate Lines does, with a checked example
This tool de-duplicates newline-separated text with controls for letter case, surrounding whitespace, and output order. It keeps the original version of the first matching line. That makes the behavior suitable for cleaning simple lists while preserving capitalization and spacing from the chosen occurrence.
Worked example
A concrete input and expected output from the current implementation.
Input
Bee Honey Bee Honey
Expected output
Bee Honey
With case sensitivity on, whitespace trimming on, and order preservation on, the second Bee and the padded Honey line match earlier normalized keys and are removed.
How the result is produced
2
A set records what has already appeared
Each normalized key is checked once in input order. Disabling order preservation sorts the surviving original lines after duplicate detection.
Good uses
- Clean copied IDs, domains, tags, or email subject lines.
- Remove repeat entries from a hand-maintained allowlist.
- Prepare a stable list before comparing two inventories.
Limits and checks
- Case-insensitive mode can merge values that a downstream system treats differently.
- Blank lines are values too and collapse to one surviving blank line.
- Sorting uses JavaScript string order, not locale-aware natural ordering.
Common questions
Which duplicate is kept?
The first occurrence is kept. Later lines with the same comparison key are removed.
Does trimming remove spaces from the result?
No. Trimming affects comparison only. The retained first line keeps its original spaces.
References and verification
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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