Duplicate Line Remover guide
Clean duplicate emails, URLs, keywords, SKUs, or names out of any list. The first copy of each line is kept in its original position, and you can ignore capitalization and stray spaces so near-duplicates are caught too.
How deduplication works here
The tool splits your text on line breaks, optionally trims each line and drops blanks, then walks the list from top to bottom. Each line is turned into a comparison key (lowercased if Ignore case is on) and checked against a set of keys it has already seen. New key: the line is kept. Seen key: the line is dropped. That is a single pass, so it stays fast even for very long lists.
Because the first occurrence wins, the original order is preserved. That matters more than it sounds: a ranked keyword list, a prioritized to-do list, or a CSV column you plan to paste back next to other data all depend on order. Sorting is available, but it is off by default for that reason.
Empty lines are dropped by default, since blank lines are almost always leftovers from copying. Untick Remove empty lines if your data uses blank lines on purpose; the tool then treats a blank line like any other value, keeping the first one and removing later repeats. The counters above the output show lines in, unique lines, and duplicates removed, so you can confirm the numbers before copying the result.
Worked example: cleaning an email list
The sample list has seven lines: [email protected], [email protected], [email protected], " [email protected]" with leading spaces, [email protected] again, a blank line, and [email protected].
With the defaults (ignore case, trim, remove empty lines), the blank line goes first, leaving six lines. [email protected] matches [email protected] once lowercased, and the second [email protected] is an exact repeat, so two duplicates are removed. Result: four unique addresses, and carol's leading spaces are gone.
Turn off Ignore case and [email protected] survives as a separate line, giving five. For email that is the wrong answer: the domain part of an address is case-insensitive, and virtually every provider treats the local part that way too. For file names on Linux or case-sensitive IDs, keep case sensitivity on.
The invisible characters that break matching
Most "it didn't remove my duplicates" problems come from characters you cannot see. Trailing spaces are the big one, especially in data exported from spreadsheets or copied from PDFs. Trim spaces handles those at both ends of each line.
Other culprits: non-breaking spaces (U+00A0) copied from web pages, tabs from spreadsheets, zero-width spaces from some rich-text editors, and Windows line endings. Line endings are handled automatically. For the rest, run the text through the whitespace cleaner first, then dedupe.
Where people use it
SEO keyword research: merging exports from several tools produces heavy overlap. Deduping before you paste into a spreadsheet saves paying for duplicate lookups in rank trackers.
Email and CRM imports: most email platforms, including Mailchimp and HubSpot, merge or reject duplicate addresses on import. Cleaning first means your contact counts, and your bill, reflect real people.
Developer chores: unique IPs from a log, unique error messages, a deduped list of package names or URLs to crawl. On the command line, sort -u file.txt does the same job but sorts; awk '!seen[$0]++' file.txt keeps order, which is exactly what this tool does.
Common mistakes
Deduping whole rows when you meant one column. If each line is a full CSV row, two rows for the same customer with different phone numbers are not duplicates. Extract the column you care about first.
Assuming case never matters. Ignore case is the right default for emails, names, and keywords, but not for passwords, API keys, or URL paths, which can be case-sensitive.
Sorting away the evidence. If you need to know which items were repeated, compare the input and output with the text diff checker before you sort.
Related tools
To order a cleaned list, use the list sorter or text alphabetizer, which offer numeric and reverse sorting. To tidy messy spacing before deduplication, use the whitespace cleaner. And to see exactly what changed between two versions of a list, paste both into the text diff checker.
Frequently asked questions
How do I remove duplicate lines from a list?
Paste the list, one item per line. The unique lines appear below as you type, with a count of how many duplicates were removed. Click Copy to grab the cleaned list.
Does it keep the original order?
Yes. The first occurrence of each line stays where it was and later copies are dropped. Tick Sort A-Z if you want the result alphabetized instead.
Are "Apple" and "apple" treated as duplicates?
With Ignore case on (the default), yes, and the first spelling is kept. Turn it off if capitalization matters, for example with case-sensitive passwords, file paths on Linux, or product codes.
Why are some duplicates not being removed?
Usually invisible differences: a trailing space, a tab, or a non-breaking space copied from a web page or spreadsheet. Keep Trim spaces on to ignore leading and trailing whitespace. Differences inside the line, such as two spaces between words, still count as different.
How do I remove duplicates in Excel or Google Sheets instead?
Excel: Data > Remove Duplicates, or =UNIQUE(A:A) in Excel 365. Google Sheets: Data > Data cleanup > Remove duplicates, or =UNIQUE(A:A). This tool is faster for lists that are not already in a spreadsheet.
How many lines can it handle?
Hundreds of thousands. It uses a hash set, so each line is checked once, and 100,000 lines typically clean in well under a second on a modern laptop or phone.
Is my list kept private?
Everything runs in your browser. Nothing you enter is uploaded to a server or stored by us.