About the Duplicate Line Remover
Paste any list — emails, URLs, keywords, product codes, log entries — and get it back with every duplicate line stripped out, keeping only the first occurrence of each. A counter reports exactly how many duplicates were found and removed, so you know the cleanup actually achieved something. Original order is preserved throughout, which matters whenever your list is ranked or chronological rather than alphabetical.
Two switches control what counts as a duplicate. Case sensitivity decides whether Apple and apple are the same entry — turn it off when deduplicating emails or domains, on when capitalisation is meaningful. Trimming ignores stray spaces and tabs around lines, catching duplicates that differ only by invisible whitespace, the kind spreadsheet exports love to create. As always on Tooldoodle, your list is processed in your browser and never uploaded.
Features
- Removes duplicate lines while keeping original order
- Shows a count of how many duplicates were removed
- Choose case-sensitive or case-insensitive duplicate matching
- Trim option catches whitespace-only differences
- Handles thousands of lines instantly
- Client-side processing — lists never leave your device
How to remove duplicate lines online
- Paste your list, one item per line.
- Decide whether matching should be case-sensitive.
- Enable trimming to ignore leading and trailing spaces.
- Run the dedupe and check how many lines were removed.
- Copy the cleaned list back to your clipboard.
Frequently asked questions
Which copy of a duplicate line is kept?
The first one. The tool scans from top to bottom, keeps a line the first time it appears and drops every later repeat, so the surviving list preserves your original ordering. If you'd rather keep a different occurrence, sort or rearrange the list before deduplicating it.
Are 'Apple' and 'apple' treated as duplicates?
That's your call. With case-insensitive matching enabled they collapse into one entry — usually what you want for emails, domains and usernames, which are case-insensitive in practice. With case-sensitive matching they stay separate, which is right for passwords, IDs and code where capitalisation carries meaning.
Why do visually identical lines survive deduplication?
Almost always invisible whitespace: one line ends with a space or tab the other lacks, often after pasting from Excel or a PDF. Switch on the trim option so surrounding whitespace is ignored during comparison. Non-breaking spaces copied from web pages can cause the same effect.
How large a list can it handle?
Tens of thousands of lines are processed in a blink, because the comparison runs directly in your browser's memory with no network round-trip. Extremely large lists in the hundreds of thousands of lines still work; the browser tab just needs a moment longer to churn through them.
Is my list private?
Yes. Deduplication happens locally in your browser — the list is never transmitted, stored or seen by anyone else. That makes the tool appropriate for customer email lists, internal hostnames and other data you're not allowed to paste into services that process text on their servers.