Remove Duplicate Lines
Remove duplicate lines from text while keeping the first occurrence — with case-insensitive matching, trimming, and empty-line removal.
About the Remove Duplicate Lines
Remove Duplicate Lines takes any block of text and strips out repeated lines, leaving a clean list with no accidental copies. Paste a list — email addresses, URLs, keywords, log entries, product SKUs, names, or CSV rows — and the tool instantly removes duplicates while keeping the first occurrence of each line and preserving the original order. When you need the opposite of a "unique" list, you can also switch modes to keep only the lines that appear exactly once, discarding every line that repeats at all.
Cleaning duplicates by hand is slow and error-prone, especially once a list runs past a screenful. Spreadsheets have a remove-duplicates feature, but opening one just to clean twenty lines is overkill, and they can reformat your entries or reinterpret them as dates and numbers. This tool keeps things simple and predictable: it treats every line as plain text, applies one clear rule, and updates the result the instant you change an option. Everything runs locally in your browser — your text is never uploaded, stored, or sent anywhere — so it is safe for private lists, internal data, or anything you would rather not paste into a website.
How to use
- Paste your text into the top box, with one item on each line.
- Choose a mode: Remove duplicates (keep one) keeps the first copy of each line, while Keep only unique lines removes every line that appears more than once.
- Toggle the options you want — case-insensitive matching, trim each line before comparing, and also remove empty lines — to control how lines are matched.
- Check the counts below the options to see how many lines were original, removed, and remaining.
- Copy the result with one click, or Clear to start over with new text.
A few notes on the options. Case-insensitive treats "Apple" and "apple" as the same line, so mixed-case duplicates are caught. Trim each line before comparing ignores leading and trailing spaces and tabs, so " report" and "report " are recognized as duplicates even though their raw text differs; the trimmed comparison also decides whether a line counts as empty. Also remove empty lines deletes blank lines entirely, which is handy when copy-pasted text arrives padded with extra line breaks. The output is copy-ready and preserves your exact line content (aside from any trimming you enabled).
Frequently asked questions
Does this tool upload or store my text?
No. All processing happens entirely in your browser using client-side JavaScript. Your text never leaves your device — nothing is uploaded to a server, saved, or shared. That makes it safe for confidential lists, internal data, personal notes, or any sensitive content you would rather keep offline.
Which copy of a duplicate line is kept?
In the default Remove duplicates (keep one) mode, the tool keeps the first occurrence of each line and removes every later repeat, so the surviving lines stay in their original order. If you instead choose Keep only unique lines, any line that appears two or more times is removed completely, leaving only the lines that showed up exactly once.
What is the difference between the two modes?
"Remove duplicates (keep one)" collapses each group of identical lines down to a single copy — you keep one of everything. "Keep only unique lines" is stricter: it throws away every line that repeats at all, so a line that appeared three times is removed entirely, not reduced to one. Use the first mode to clean a list, and the second to find the truly one-off entries.
How do the case-insensitive and trim options affect matching?
Both change how two lines are compared. With case-insensitive on, letter casing is ignored, so "Email" and "email" match. With trim on, spaces and tabs at the start and end of each line are ignored before comparing, so " item" and "item " match. You can combine them, and either can be left off when exact, character-for-character comparison matters.
What do the counts mean?
The counts summarize the result: Original is the number of lines you pasted, Removed is how many lines were dropped (duplicates, and empties if that option is on), and Remaining is how many lines are in the output. They update live as you edit the text or change any option, giving you a quick sense of how much was cleaned.
Can I process a very long list?
Yes. There is no fixed line limit, and because the work runs locally the tool handles thousands of lines quickly. Extremely large pastes depend on your device's available memory, but ordinary lists — even long ones — deduplicate almost instantly.