Free Remove Duplicate Lines Online
Remove duplicate lines from multi-line text. Case-insensitive and trim options available. Everything runs in your browser.
The Remove Duplicate Lines tool strips repeated lines from multi-line text, with case-insensitive and trimming options. Everything runs in your browser, so the text stays on your device.
Free online duplicate line remover tool
This tool scans multi-line text and removes duplicate lines while preserving the original order by keeping only the first occurrence of each unique line. It uses a JavaScript Set to track which lines have already appeared, giving you deterministic deduplication regardless of how large the input is. It is useful for cleaning lists of email addresses, IP addresses, domain names, or code entries, where it identifies and strips the repeats so you are left with a clean, unique dataset ready to paste back into a spreadsheet, a configuration file, or a data pipeline without any manual sorting.
Two optional switches change how lines are compared before deduplication. Case-insensitive comparison treats entries like "EXAMPLE" and "example" as the same line by converting each to lowercase before the lookup, which is especially useful for email addresses and file paths that are frequently mixed in capitalization. The trim option removes leading and trailing whitespace, so lines that differ only by surrounding spaces, such as a padded " line " and a plain "line", are also merged. Internally each line is passed through the selected transformations and then checked against the Set, so the result stays predictable and the order of first appearance is always preserved.
All processing happens entirely in your browser using a pure JavaScript function that maintains no server-side state. Your text never leaves your device, and nothing is uploaded or stored after you close the page, which makes it a safe fit for lists that may contain personal or internal data. There are no file-size limits, no upload step, and no registration, and because it runs from static JavaScript it even keeps working offline once the page has loaded, so you can clean up data on any device with a modern browser.
How to use this Remove Duplicate Lines tool
- Paste or type your multi-line text into the input box above.
- Enable "Case-insensitive" to treat "Text" and "text" as duplicates.
- Enable "Trim whitespace" to remove leading/trailing spaces before comparison.
- The deduplicated text appears instantly below with a count of removed duplicates.
- Click the result to copy it back to your clipboard.
FAQ
What does this duplicate line remover do?
This tool scans multi-line text and removes duplicate lines, keeping only the first occurrence of each unique line.
Is my data safe when using this tool?
Yes. All processing happens entirely in your browser. No data is sent to any server, and nothing is stored after you close the page.
Can I use this tool for code cleanup?
Absolutely. It works great for removing duplicate import statements, config entries, or any repetitive code patterns from source files.
What are case-insensitive and trim options?
Case-insensitive treats "Line" and "line" as duplicates. Trim removes leading and trailing spaces before comparing lines, so " line " and "line" are considered duplicates.