Keycloak - Open Source Identity and Access Management for modern Applications and Services.
SaaSiter Contacts Importer - Allow users to import contacts into their system.
Auth0 - Auth0 is a program for people to get authentication and authorization services for their own business use.
CloudSponge - Companies from every industry use CloudSponge’s Contact Picker to get access to their users’ address books.
1Password - 1Password can create strong, unique passwords for you, remember them, and restore them, all directly in your web browser.
OpenInviter - OpenInviter is a free import contacts (addressbook) script from email providers like Mail2World...