Compare Two Lists

About the Compare Two Lists

Paste one list on the left and another on the right to see, at once, the items only in A, only in B, in both and in either (the union), each with a count. The order of each list doesn’t matter: unlike a line-by-line diff, this compares the lists as collections, so “banana” is found no matter where it sits.

Choose whether Apple and apple are the same item, whether spaces around items count, and whether repeats matter. With Ignore duplicates on, each list is treated as a set; turn it off to compare quantities — three copies of an item in your stock against one in the orders leaves two over. Items can be one per line, or separated by commas, semicolons, tabs or spaces, and the full comparison exports to a CSV with each item’s count in both lists.

Common uses

• Mailing lists: subscribers minus unsubscribes or bounces, or the contacts that appear in both of two exports.
• Social media: accounts you follow that don’t follow you back, from two exported lists of usernames.
• Inventory: stock against orders, or a delivery note against a purchase order, with quantities.
• Data checks: which IDs, SKUs or invoice numbers are missing from one system compared with another.

What each result means

• Only in A — items of List A that do not appear in List B (A minus B, the set difference).
• Only in B — items of List B that do not appear in List A.
• In both — items that appear in both lists (the intersection).
• All items — every item from either list, once each (the union).

Results keep the order in which items first appear — List A first, then the new items of List B — unless you sort them. When the same item is written differently (for example Apple and apple with Ignore case on), the result shows it the way it is first written.

Similarity is the Jaccard index: the number of distinct items in both lists divided by the number of distinct items in either. 100% means the two lists hold exactly the same items.

Duplicates and quantities

With Ignore duplicates on (the default), a repeated item counts once, as in a set: three copies of “pen” in List A and one in List B means “pen” is in both, and nothing is left over.

With it off, every copy counts, as in a multiset (a bag). Copies are paired one-to-one: three “pen” in A and one in B gives one “pen” in both and two “pen” only in A. All items then holds the larger number of copies of each item. The counts under each list show how many items it has, how many are distinct and how many are repeats.

How items are matched

Two items match when they are the same text after the options you chose: Trim spaces ignores spaces and tabs around an item, and Ignore case uses full Unicode case folding (so STRASSE and straße match). Letters with accents match however they were typed — as one character or as a letter plus a combining accent. Everything else must be identical: colour and color, or Ltd and Limited, are different items.

Limitations

• Near-matches (typos, abbreviations, different spellings) are not detected; clean the lists first with Find and Replace if they use different conventions.
• Quotation marks are not treated specially: with commas as the separator, "Smith, John" becomes two items. Use one item per line for items that contain the separator.
• To compare two versions of a document line by line (with changes shown in place), use Text Diff; for spreadsheets with many columns, use Spreadsheet Compare.

Privacy

Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot.