Remove Duplicate Lines
Paste a list of lines and get only the unique ones — with fine control over whitespace trimming, case sensitivity, and which duplicate (first or last) to keep.
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Related cleanup & transforms tools
Deduplication Guide
Why deduping is a daily SEO task
Scraped keyword lists, exported URLs, email collections, backlink exports — they all come back with duplicates. Cleaning them is the first step before any real analysis. This tool does it in one paste.
Keyword research cleanup
SEO tools often export overlapping keyword sets. Paste the combined list, dedupe, and you immediately see your true unique keyword pool. Saves minutes every time you do research.
URL list cleanup
Crawlers return the same URL with and without trailing slashes, with different UTM parameters, or in different cases. Paste your URL list, enable trim + case-insensitive, and get a clean canonical list.
Email list dedupe
Running an outreach campaign? Dedupe your email list before import — duplicate sends look spammy and damage sender reputation. Case-insensitive mode catches 'Bob@Example.com' vs. 'bob@example.com'.
Keep first vs. keep last
Most of the time 'keep first' is what you want — the original appearance. 'Keep last' is useful when your list is ordered newest-first and duplicates should prefer the most recent entry.
Trim whitespace
Pasted lists often have trailing spaces that make lines look unique when they aren't. 'Trim each line' normalizes them before comparing — and usually finds duplicates that looked unique.
Safe and local
Lines are deduped in your browser — perfect for confidential data like customer emails, internal URLs, or any list you can't upload to a third-party tool.
Pro Tips
This tool keeps the original line order intact. If you want alphabetical or length-sorted output instead, pipe the result through our Sort Lines tool.
URL paths are technically case-sensitive on Linux servers. Leave case-sensitive ON when deduping URLs if you want to preserve the distinction (or your server does).
By default, empty lines count as duplicates and get collapsed to a single blank line. Toggle 'keep empty lines' to preserve structure for paragraph-separated lists.
Frequently Asked Questions
- Is the line order preserved?
- Yes — output follows the original order, with duplicates stripped based on your "keep first / keep last" choice. If you need the output sorted, use our Sort Lines tool after.
- How many lines can I paste?
- Hundreds of thousands of lines work fine — the algorithm uses a hash set (O(n) time). You'll hit browser memory limits long before the algorithm slows down.
- What counts as a duplicate?
- Exact character match by default. Turn on "trim each line" to ignore leading/trailing whitespace, and turn off "case sensitive" to ignore capitalization. Combine both for the most aggressive dedupe.
- Why are blank lines showing up?
- If you enabled 'keep empty lines', blank separators pass through. Turn it off to strip all empty lines. If you want empty lines collapsed but one preserved between groups, use Text Cleaner's 'remove empty lines' instead.