Compare Two Lists takes two lists of items — email addresses, SKUs, usernames, IDs, URLs, anything one-per-line — and answers the membership questions you actually have about them: which items appear in both, which are only in the first, which are only in the second, and which are duplicated within a single list. It is set arithmetic with a UI, running instantly on lists of thousands of items.
This is not a line-by-line diff. A diff cares about order and position, so moving one line makes everything below it look changed. This tool treats each list as an unordered bag of items, which is the right model when you are reconciling an export from one system against an export from another. Row 300 in your CRM export has no relationship to row 300 in your billing export; the only thing that matters is whether the value exists on both sides. If you want a positional, side-by-side comparison of prose or code, use the Text Diff Checker instead.
Everything runs in your browser. That matters more here than for most utilities, because the lists people compare are usually the sensitive kind — customer emails, employee IDs, license keys, account numbers. Nothing is uploaded, so pasting a subscriber export into this page carries none of the risk of pasting it into a service that processes it server-side.
Put one list in List A and the other in List B. One item per line is the default; load the sample if you want to see how duplicates and case differences are reported.
Switch the delimiter to comma, semicolon, space or tab if your data is not one-per-line. A single CSV column pasted straight from a spreadsheet is usually newline-separated already.
Decide whether case matters, whether to trim surrounding whitespace, and whether to skip blank entries. Case-insensitive matching with trimming is the sensible default for emails and identifiers.
Press Compare, then open any result group — In Both, Only in A, Only in B, Duplicates — and copy it or download it as a .txt file. Copy Report exports every group at once.
One comparison gives you intersection, both differences, the symmetric difference and the union — no need to re-run the tool with a different mode selected for each question.
Items repeated inside a single list are reported separately from cross-list matches, which catches the double-entry problem that causes duplicate sends and double-billing.
Fold case for matching so Erin@ and erin@ count as one item, while the output still shows the original casing exactly as you pasted it rather than a lowercased copy.
Newline, comma, semicolon, space or tab. Paste a spreadsheet column, a CSV row or a space-separated shell output without reformatting it first.
Compare two texts and find differences. Highlight additions, removals, and common parts with word or character level comparison.
Compare two JSON documents structurally and see added, removed, and changed keys with exact paths
Count words, letters, sentences, paragraphs, and estimate reading time
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