Names, organisations, emails, phones, addresses, tags and notes, kept in this browser. Import the .vcf your phone or mail client already exports, or a CSV; export the same way, one contact or all of them. Free, no account, nothing uploaded.
vCard (.vcf) is what phones and mail clients speak; CSV is for spreadsheets; JSON is the copy you load back here. Imports skip contacts that are already in the list.
They live in this browser. Saved on every change to this browser's local storage on this device. Clear the browser's site data and they are gone, so export a copy of anything that matters.
Nothing is sent anywhere. No account, no sync, no address book harvesting. To carry contacts to a phone, export a .vcf and open it there.
vCard support is the common core. Name, organisation, role, one email, one phone, one address, categories and a note. A card with several phone numbers keeps the first.