What the Remove Duplicate Lines does
This tool removes repeated lines from any text in one step. Paste an email list, a list of keywords, product codes, URLs or a column copied from Excel or Google Sheets, and you immediately get a clean list in which every entry appears only once. A short summary shows how many lines you started with, how many unique lines are left and how many were removed.
Unlike sorting tools, it keeps your original order: the first time a line appears it stays exactly where it was, and only later repeats are deleted. Three options let you decide what counts as a duplicate — whether “Apple” and “apple” are the same, whether spaces at the start and end of a line matter, and whether empty lines should be dropped.
Your text is processed locally in your browser and never uploaded, so you can safely clean lists of customer emails or other personal data.
When to use it
Email and contact lists
Remove addresses that appear twice before importing a list into your newsletter tool or CRM.
SEO keyword research
Merge keyword exports from several tools and keep each keyword only once.
Spreadsheets
Copy a column from Excel or Google Sheets, remove duplicates here and paste it back.
Logs and code
Reduce repeated log lines, imports or configuration entries to see what is really there.
Tips for the best results
- Turn on “Ignore upper/lower case” for email addresses and domain names, which are not case-sensitive in practice.
- Keep “Trim spaces” switched on: invisible spaces at the end of a line are a common reason why duplicates are not recognized.
- Need the list sorted as well? Remove duplicates first, then paste the result into our line sorter.
- To find duplicates across two lists, paste both lists one below the other.
How the Remove Duplicate Lines works
The text is split into lines at every line break (Windows, Mac and Linux line endings are all recognized). Each line is optionally trimmed and, if you ignore case, converted to lowercase using your language’s rules to create a comparison key.
The tool walks through the lines from top to bottom and remembers every key it has already seen in a set. A line whose key is new is kept; a line whose key was seen before is skipped. This takes only a fraction of a second even for lists with hundreds of thousands of lines.
The original spelling of the first occurrence is kept in the result, so ignoring case never changes how your entries are written.