Duplicate Line Finder
Paste your text and instantly see which lines appear more than once, along with their counts. Perfect for cleaning up mailing lists, finding repeated entries in logs, or verifying data uniqueness. No signup, no uploads — everything stays private in your browser.
Why use this Duplicate Line Finder?
Manually scanning a list for repeated lines is tedious and error‑prone. Our tool instantly counts every line and highlights those that appear more than once, so you can quickly spot duplicates in mailing lists, log files, CSV data, or any text list. Because processing stays in your browser, your sensitive data never leaves your device.
- Instant counts – see exactly how many times each duplicate line appears.
- Flexible matching – trim whitespace, ignore case, or skip blank lines to fit your data.
- Clean output – only duplicate lines are shown, sorted by frequency (most common first).
- Privacy first – all processing is done locally; your text never touches a server.
How to find duplicate lines (step‑by‑step)
1. Paste your list
Drop any text list into the left box — each line is treated as a separate entry.
2. Adjust matching rules
Trim spaces, ignore case, or exclude blank lines. The tool updates automatically.
3. View duplicates
All repeated lines appear on the right with their count (e.g., "apple (3 times)"). Lines that appear only once are hidden.
4. Copy or clear
Use "Copy List" to grab the formatted duplicates for documentation, or "Clear All" to start fresh.
Example: cleaning a mailing list
| Input (list) | Duplicate Lines Found |
|---|---|
| john@example.com jane@example.com john@example.com bob@test.com jane@example.com john@example.com | john@example.com (3 times) jane@example.com (2 times) |
Common use cases
- Mailing list cleanup: Identify duplicate email addresses before sending campaigns.
- Log analysis: Spot repeated error messages or recurring events.
- Data deduplication: Find duplicate entries in CSV columns, product lists, or usernames.
- Inventory check: Count how many times each item appears in a stock list.
- Code review: Detect duplicated import statements or configuration lines.
Pro tips
- Enable "Trim whitespace" to treat
"apple "and"apple"as the same line. - If your list is case‑sensitive (e.g., part numbers), leave "Case‑insensitive" unchecked.
- After identifying duplicates, use the Duplicate Line Remover to remove them automatically.
- The output is sorted from most frequent to least frequent, making it easy to prioritize the biggest offenders.