How do I find items that are in one list but not the other?

The "Only in A" and "Only in B" groups answer that, and they're deliberately separate. Only in A holds items missing from List B; Only in B holds items missing from List A. These are usually different problems with different causes — missing-from-billing and missing-from-CRM aren't the same bug — so collapsing them into one answer loses the information you need. The "Unique" group combines both if you want the symmetric difference.

Can it find duplicates inside a single list?

Yes. Duplicates in A and Duplicates in B list every distinct item appearing more than once within that list. This is independent of cross-list matching, so an item can be both duplicated in A and present in B. It's usually the check that matters most in practice, since within-list duplicates are what cause duplicate emails and double-billing.

Does capitalisation affect the comparison?

Only if you want it to. Case-sensitive matching is off by default, so Erin@toolz.dev and erin@toolz.dev are treated as one item — and the output preserves whichever form you pasted rather than lowercasing your data. Turn it on for values where case carries meaning: Linux paths, base64 strings, hashes, API keys, Git SHAs.

What's the difference between this and a text diff tool?

A diff is positional: it compares line 1 to line 1 and computes the edits needed to turn one sequence into the other, so reordering a list makes nearly every line look changed. This tool ignores order entirely and only asks whether an item exists on each side. Use a diff for code and prose where position is meaning; use list compare for reconciling exports where the sort order is arbitrary.

Can I compare lists separated by commas instead of new lines?

Yes — switch the separator to comma, semicolon, space, or tab. Whitespace around each item is trimmed by default, so a, b, c splits into three clean items. One caveat: splitting on commas isn't real CSV parsing, so if your data has quoted fields containing commas, extract the column with a proper CSV tool first.

How many items can it handle?

The comparison indexes each list into a hash map and runs in linear time rather than using nested loops, so tens of thousands of items on each side complete in milliseconds. The practical ceiling is your browser rendering a very large result group into the page, not the comparison itself.

Are my lists uploaded anywhere?

No. All parsing and comparison happens as JavaScript in your browser — nothing is transmitted, logged, or stored. This matters here more than for most tools, because the lists people reconcile are usually customer emails, employee IDs, or license keys. Watch your network tab while comparing, or go offline and it keeps working.

Compare Two Lists: Find Common Items, Unique Items, and Duplicates

Toolz Team

|Jul 21, 2026|3 min read

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Related tools: Text Diff Checker when order and position matter, JSON Diff for structured data, CSV Viewer for extracting a column from a real CSV, and Word Counter for quick counts. Further reading: why browser-based tools beat server-side ones and the web developer's toolkit.

Frequently Asked Questions

Paste one list into List A, the other into List B, and press Compare. The "In Both" group is the intersection — every item present in both lists. You can copy that group on its own, download it as a text file, or export every group at once with Copy Report. Order doesn't matter, so the lists don't need to be sorted the same way.

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Compare Two Lists: Find Common Items, Unique Items, and Duplicates

Frequently Asked Questions

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