List Compare
Compare two lists to find common items, differences, and duplicates — union, intersection, only-in-A, only-in-B, and symmetric difference.
About this tool
The List Compare tool runs set operations on two lists of text — anything you can paste as one item per line: user IDs, email addresses, URLs, file names, SKUs, tags. It answers questions like "which IDs are in both lists?", "what did I add to list B?", or "what's missing from list A?"
Pick an operation and the result appears instantly. The seven operations cover the standard set vocabulary: Union (everything in either list), Intersection (items in both), Only in A and Only in B (set differences), Symmetric difference (items in exactly one list), and Duplicates (lines that appear more than once within a single list).
Examples:
- List A
1, 2, 3, 4, List B3, 4, 5, 6→ Intersection →3, 4 - List A
1, 2, 3, 4, List B3, 4, 5, 6→ Only in A →1, 2 - List A
1, 2, 3, 4, List B3, 4, 5, 6→ Symmetric diff →1, 2, 5, 6
FAQ
What is the difference between "Only in A" and "Symmetric diff"? ›
"Only in A" returns items that appear in list A but not in list B. "Symmetric difference" returns items that appear in exactly one of the two lists — it is the union of "Only in A" and "Only in B" combined.
Does the tool treat items case-sensitively? ›
By default, yes: Apple and apple are different items. Tick "Ignore case" to treat them as equal — the result keeps the first-seen spelling. Whitespace is trimmed by default so accidental trailing spaces do not create phantom mismatches.
What does "Keep input order" do? ›
When checked (default), results follow the order items first appear in your input. When unchecked, results are sorted alphabetically, which makes it easier to eyeball or diff two output lists.
Are duplicate entries within a single list preserved? ›
No — the set operations (union, intersection, difference, symmetric difference) de-duplicate by design, because sets contain each item at most once. Use the "Duplicates in A" / "Duplicates in B" buttons to find lines that repeat within a single list.