🗑️ Duplicate Line Remover

Remove duplicate lines and keep unique lines only. Choose to keep the first or last occurrence — instant, in-browser, no upload.

Input

Keep: Case-insensitive Trim whitespace before comparing

Output

About the Duplicate Line Remover

This tool strips duplicate lines from your input and returns only the unique ones. You can choose to keep the first occurrence (default, preserves original top-down order) or the last occurrence of each duplicate. Optional toggles let you compare case-insensitively and trim whitespace before comparison — handy when messy spacing or capitalization shouldn't count as differences.

Use it to clean exported lists, dedupe CSV row labels, or build a unique vocabulary from raw text. The original line content is preserved verbatim in the output; only duplicate rows are removed.

How it works

Lines are split on newlines. A comparison key is derived from each line — optionally trimmed and lowercased based on your toggles.
A Set tracks keys already seen. In "keep first" mode, a line is emitted only if its key hasn't been seen; in "keep last" mode, the last occurrence wins by iterating from the end.
Output preserves the original (untrimmed, original-case) text of the lines that survived.

How to use the deduper

Paste your text in the input box.
Choose whether to keep the First or Last occurrence of each duplicate.
Optionally toggle Case-insensitive and Trim whitespace before comparing.
Click Remove Duplicates, then Copy the result or Clear to start over.

Frequently asked questions

Does it consider line endings when comparing? No. Lines are compared by content after newline splitting. Trailing \r from Windows line endings is stripped before comparison.

Are empty lines removed? Only if duplicates of each other. The first empty line is kept; subsequent empty lines are removed as duplicates. Use the trim option to also collapse whitespace-only lines together.

Does it upload my text? No. All deduplication happens locally in your browser. Your text never leaves your device.

Does it preserve order? Yes. "Keep first" preserves the original order of first occurrences; "keep last" reverses input order (last occurrences first), then re-reverses to restore the natural sequence.