Put one item per line in each box. Items only in the second list show in green, items only in the first show in red, and everything present in both is left plain.
The comparison reads in order, so if the same names appear in a different order the tool reports them as changes. Sorting both lists alphabetically first gives you a clean answer about what is genuinely missing or new.
Checking an attendee list against last year's, finding which email addresses were added to a mailing list, comparing an inventory count against the system, reconciling two guest lists, and spotting which items are missing from a delivery.
Yes. Lists of names, emails and phone numbers are personal data. Nothing is uploaded here — the comparison happens inside your own browser and nothing is stored anywhere.