How to compare two lists
- Paste the first listPut one list in the List A box, one item per line. You can also open a .txt or .csv file.
- Paste the second listPut the other list in the List B box. The results update as you type.
- Copy the result you needSee what is only in one list, in both, or duplicated, and copy or download any result.
Everything you need to compare lists
Differences and matches
Instantly see the items that are only in list A, only in list B and in both lists.
Find and remove duplicates
See which items repeat in each list, and get a merged list with every item exactly once.
Any separator
Split items by new line, comma, semicolon or tab, so you can paste columns from Excel or CSV files.
Ignore case and spaces
Treat “Apple” and “apple ” as the same item when capitalization and extra spaces don't matter.
Fast with huge lists
Compares lists with hundreds of thousands of items in a fraction of a second.
100% private
Nothing is uploaded. Customer lists, emails and IDs never leave your device.
What people use it for
Email and customer lists
Find which contacts are new, which unsubscribed and which appear in both lists.
Excel and spreadsheet columns
Paste two columns to see which values are missing from the other column, without formulas.
Inventory and product IDs
Compare SKUs, order numbers or IDs from two systems to find what doesn't match.
Remove duplicates
Paste one list into List A to see its duplicates and copy a clean list with each item once.
Names and attendance
Check who registered but didn't attend, or who is on one team list but not the other.
URLs and keywords
Compare two lists of URLs, keywords or domains to find gaps and overlaps.
Frequently asked questions
How do I compare two lists?
Paste the first list into List A and the second into List B, one item per line. DiffDuo instantly shows the items only in List A, only in List B, in both lists, and the duplicates in each.
How do I find duplicates between two lists?
The items that appear in both lists are shown under In both lists. You can copy them with one click or download them as a .txt file.
How do I remove duplicates from a list?
Paste the list into List A and leave List B empty. All unique items shows every item exactly once, and Duplicates in List A shows the items that were repeated.
Can I compare two columns from Excel?
Yes. Copy a column from Excel or Google Sheets and paste it into List A, then paste the other column into List B. Each cell becomes one item.
Can I use commas or semicolons instead of new lines?
Yes. Choose comma, semicolon or tab under Split by. New lines always separate items too.
Is the comparison case-sensitive?
By default, yes. Turn on Ignore case to treat uppercase and lowercase letters as the same. Trim spaces ignores spaces at the start and end of each item.
Are my lists uploaded anywhere?
No. The comparison runs entirely in your browser, so your lists never leave your device.