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Keep Only Duplicate Lines
Paste text to keep only duplicate lines from your input. Detect repeated lines, keep one copy or all duplicate occurrences, optionally include counts, and preserve original line text and order. All processing runs locally in your browser.
Paste your text below to keep only duplicate lines. The tool compares lines in order, ignores empty lines, and returns duplicated lines only.
⚙ Options
No input yet.
⭐ About Keep Only Duplicate Lines
The Keep Only Duplicate Lines tool scans your text line by line and returns only lines that appear at least 2 times. It preserves original line text exactly in output and ignores empty lines automatically.
⚙️ How duplicate line detection works
- A line is a duplicate when it appears 2 or more times.
- Empty lines are always ignored and never included in output.
- Matching is case-sensitive by default.
- Output order follows the first occurrence order of each duplicate line group.
⚙️ Available options
- Keep one copy of each duplicate line: output each duplicate group once.
- Disabled Keep one copy: output all occurrences of duplicated lines in original order.
- Include count: append count like
line text (3 times). - Case-insensitive mode: treat
Appleandappleas duplicates. - Trim whitespace: ignore leading/trailing spaces when comparing lines.
🔎 Example
Input:
apple banana apple orange banana banana
Output (Keep one copy enabled):
apple banana
Output (Keep one copy disabled):
apple banana apple banana banana
Output (Keep one copy enabled + Include count):
apple (2 times) banana (3 times)
🔎 Common use cases
- Keep only repeated values from large lists.
- Find duplicate entries before imports and merges.
- Extract repeated log messages from diagnostic files.
- Review duplicated keywords or tags in content datasets.
⚠️ Notes
- All processing happens in your browser for privacy.
- Line text is returned exactly as it appears in your input.
- Copy and Download .txt export exactly what is shown in output.
Frequently Asked Questions
It analyzes multiline text and returns only lines that appear at least twice.
A line is considered a duplicate when the same comparable value appears 2 or more times in the input.
No. Empty lines are always ignored and never included in output.
Yes. With Keep one copy enabled, each duplicate group appears once, in first-occurrence order.
The tool outputs all occurrences of duplicated lines, preserving the original input order.
Yes. Enable Include count to append values like line text (3 times).
Yes by default. Enable Case-insensitive mode to treat Apple and apple as duplicates.
Yes. Enable Trim whitespace to compare trimmed values while keeping original output text unchanged.
Yes. Output lines keep original text exactly, with no normalization unless you add count text.
Yes. You can upload a TXT file, then use Copy or Download .txt for the resulting duplicate lines.
No. All duplicate line analysis runs locally in your browser and your content is not uploaded.