List Comparer
Compare two lists and see what is in both, only in A, or only in B — instantly.
0 unique in A · 0 unique in B · 0 in both · 0 only in A · 0 only in B
How it works
Paste one list into box A and another into box B — the comparison runs instantly as you type. Each list is read one entry per line, blank lines are ignored and repeated entries inside the same list are collapsed, so the tool compares them the way you would think of them: as two sets. The summary line always shows how many unique entries each list has, how many appear in both, and how many are only in A or only in B, while the Show menu picks which of those groups lands in the result box — common entries, what is missing from one side, the full set of differences, or the merged union of both lists.
Turn on Ignore case when "Apple" and "apple" should count as the same entry, keep Trim spaces on so stray leading or trailing whitespace from a spreadsheet paste does not hide a match, and use Sort A → Z if you want the output alphabetised instead of in its original order. Swap A and B flips the two boxes so you can check the other direction in one click.
Everything is plain JavaScript running in your browser — nothing is uploaded, so it is safe for email lists, customer IDs, SKUs, keyword sets and other confidential data. Copy the result to the clipboard or download it as a .txt file when you are done.
Frequently asked questions
How do I compare two lists to find what they have in common?
Paste one list into box A and the other into box B, one entry per line. The comparison runs as you type and the Show menu is set to "In both lists" by default, so the common entries appear in the result box immediately. The summary line underneath also tells you how many unique entries each list has and how many overlap.
How do I find what is in list A but not in list B?
Choose "Only in list A (missing from B)" in the Show menu. Pick "Only in list B" for the opposite direction, "Only in A or only in B" for every difference at once, or "All entries from both lists" for the merged union. The Swap A and B button flips the boxes if you want to check the other direction without re-pasting.
Can it ignore capitalisation, extra spaces and duplicate entries?
Yes. Trim spaces on each line is on by default, so entries pasted from a spreadsheet still match, and blank lines are always ignored. Tick Ignore case to treat "Apple" and "apple" as the same entry. Repeated entries inside the same list are collapsed automatically, so the two lists are compared as sets rather than as raw lines.