Compare Two Lists Tool Online
Compare two lists instantly - difference, intersection, symmetric difference, union - with case and whitespace controls. Free, client-side, offline.
Paste two lists and instantly find their difference, intersection, symmetric difference, or union — with full control over case, whitespace, and separators.
How to Use Compare Two Lists Tool Online
- Paste List A into the left textarea and List B into the right. One item per line is the most common - but you can use any separator (comma, semicolon, tab, pipe, space) by picking it from the Input separator dropdown.
- Pick the comparison mode: A - B and B - A find items unique to one list, A ∩ B finds the overlap, A ⊕ B (symmetric difference) finds everything except the overlap, and A ∪ B merges both into a single deduped list.
- Choose the output separator independently of the input - paste a comma-delimited CSV and export the diff as newline-per-line, or vice versa. By default the output separator mirrors the input.
- Flip the toggles: enable Case sensitive when
Appleandappleshould be counted as different; enable Trim whitespace (on by default) so" apple "matches"apple". - Hit Compare (or press
Ctrl+Enter/⌘+Enterfrom anywhere on the page). The stats line reports how many items each list contained, how many were unique after dedupe, and how many landed in the result. - Copy the result to the clipboard, or Download .txt to save a timestamped file named
compare-lists-<mode>-<iso>.txt- useful when comparing multiple pairs in sequence without overwriting. - Clear all wipes both lists, the output, and returns every option to its default for the next pair.
Frequently asked questions
Is my data secure when comparing lists?
Yes. Every parse, set build, and comparison runs in your browser with vanilla JavaScript – nothing is uploaded, cached, or tracked. After the page loads you can disconnect from the network and keep comparing lists indefinitely.
Is this list comparison tool free?
Yes, 100% free with no cap on list size or number of comparisons. No sign-up, no watermark, no premium tier.
Does this work offline?
Yes. Once the page has loaded, the HTML, CSS, and JS are self-contained. Turn off Wi-Fi and the Compare button keeps working.
What comparison modes are available?
Five set operations: A – B (items only in List A), B – A (items only in List B), A ∩ B (items in both lists), A ⊕ B (symmetric difference – in either list but not both), and A ∪ B (union – all unique items from both lists combined).
Can I use different input and output separators?
Yes. The Input and Output separator dropdowns are independent – paste a comma-separated CSV, pick Newline as the output, and the result is one item per line. By default the output mirrors the input, but change it any time.
How are duplicate items inside a list handled?
Each list is treated as a set before comparison, so duplicates collapse to one entry. If List A contains apple, apple, banana, the tool sees {apple, banana} – the stats line shows both the raw input count and the unique count so you can spot heavy duplication.
Does case matter when comparing?
By default no – Apple and apple match. Enable Case sensitive if you need them to be different. The result preserves the casing of the first occurrence seen, so the output still looks natural.
What is the maximum list size?
There is no hard cap. The comparison uses native Set operations, so 10 000 items per list finishes in well under a second on a typical laptop. Very large pastes still run synchronously – no spinner needed.
What does symmetric difference mode do?
Symmetric difference (A ⊕ B) returns items that are in exactly one list – the opposite of intersection. Think of it as “find everything that differs between these two datasets” in a single click.
Can I use this to deduplicate or merge lists?
Yes. Pick A ∪ B (union) and the result is a single list containing every unique entry from both inputs – useful for merging contact lists, email exports, or any two datasets where you want one deduped master.