Duplicate Line Remover
Paste any list — emails, keywords, URLs, imports — and remove every repeated entry. See exactly what was removed and optionally sort the result alphabetically.
Paste any list — emails, keywords, URLs, imports — and remove every repeated entry. One item per line.
How to use the duplicate line remover
Paste your list into the editor — one item per line. The deduplicated result appears immediately in the output panel, along with a count of how many lines were removed. The removed-entries panel shows exactly which lines were stripped. When you're satisfied, click Replace to swap the clean list back into the editor.
How duplicate detection works
Each line is compared against all previously seen lines. If a match is found, the duplicate is discarded. The first occurrence of each entry is always kept. With “trim whitespace” enabled, lines are stripped of leading and trailing spaces before comparison — so “ apple” and “apple” are treated as the same entry.
Common uses for deduplication
Deduplication is a recurring task in data work. Email marketers remove duplicate addresses before sending campaigns. SEO teams clean keyword lists exported from multiple tools. Developers deduplicate npm packages or import paths. Content teams consolidate URLs from multiple crawl exports. Any time two sources are merged, a deduplication pass is the first clean-up step.
Frequently asked questions
What kind of lists work best with this tool?
Any list where one item = one line: email addresses, domain names, keywords, product SKUs, usernames, hashtags, CSS class names, file paths, or any exported CSV column. Paste the list, click Copy or Replace, and you have a deduplicated version. The case-insensitive option is important for email lists — 'User@example.com' and 'user@example.com' are the same address and should be treated as duplicates.
Does it preserve the original order of items?
Yes, by default. The first occurrence of each line is kept; later duplicates are removed. The order of the first appearances is preserved. If you check 'Sort A→Z', the output is sorted alphabetically after deduplication. If you need the original order preserved, leave 'Sort' unchecked.
What does 'ignore surrounding spaces' do?
It trims leading and trailing whitespace from each line before comparing. So ' hello ' and 'hello' are treated as the same line. This is useful for lists pasted from spreadsheets, where cells may have trailing spaces that are invisible but cause false negatives in exact matching.
What is the 'Show only duplicates' mode for?
It inverts the operation — instead of showing the cleaned list, it shows only the lines that were duplicated. Useful for auditing: you can see exactly which entries appeared more than once before deciding how to handle them. Use this on a keyword list to find which terms you accidentally added twice, or on a guest list to catch double entries.
Can I deduplicate a list with 10,000 lines?
Yes. The deduplication algorithm runs entirely in the browser with no server round-trip. It uses a JavaScript Set for O(n) performance, so even 50,000-line lists process in under a second on a modern device. There's no practical size limit within normal browser memory constraints.
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