How duplicates are found
Each line is compared with every line before it. If it's been seen already, it's dropped, so the first copy stays in its original place and the order of your list doesn't change.
With Ignore case on, “Anna@example.com” and “anna@example.com” count as the same line, and the first spelling is the one kept. With Ignore spaces on, stray spaces at the start or end of a line don't stop two lines from matching, which catches a lot of copy-paste mess.
Three ways to keep lines
The Keep option changes what you get back:
- One of each: every line once, in the original order. This is what most people want.
- Only unique lines: drops every line that appears more than once, keeping only the ones that were never repeated.
- Only the repeats: lists each line that was doubled up, once, so you can see what was duplicated.
Common uses
Cleaning an email list before an import, merging two lists of followers or customers, tidying keyword lists for ads or SEO, removing repeated links from a link-in-bio export, and checking a guest list for people who signed up twice.
To compare two lists, paste both into the box, one after the other, and choose Only the repeats. You'll see every line that's on both lists (as long as neither list repeats itself).
Doing it in Excel, Google Sheets or code
In Excel, select the column and use Data → Remove Duplicates. In Google Sheets, use Data → Data cleanup → Remove duplicates, or =UNIQUE(A:A) to get the unique values in a new column. On the command line, sort -u removes duplicates but changes the order, while awk '!seen[$0]++' keeps it.
This tool is quicker when the list isn't in a spreadsheet yet, and nothing you paste leaves your browser.
Frequently asked questions
Does it keep the original order?
Yes. The first time each line appears, it stays in place. Later copies are removed. Use the sort lines tool afterwards if you want it in A to Z order.
How do I remove duplicates but ignore capital letters?
Turn on Ignore case. “Apple”, “apple” and “APPLE” then count as one line, and the first spelling is kept.
Can I see which lines were duplicated?
Yes. Choose Only the repeats and you get each repeated line once. The Lines repeated count shows how many there are.
Is there a limit on how many lines I can paste?
No set limit. Tens of thousands of lines work fine, since everything runs in your browser.
Is my list sent anywhere?
No. The tool runs entirely in your browser. Nothing is uploaded or saved, which matters for email lists and customer data.