When you have both SharePoint Server and Office 365, by default users have a different profile in each location. This can lead to a confusing profile experience for your users. With hybrid profiles, user have a single profile where they can maintain all of their profile information.
Profile redirection in SharePoint hybrid deployments
Hybrid profiles redirects hybrid users to their profiles in Office 365. This ensures that hybrid users have a single place for their profile information. Hybrid profiles is available with both SharePoint Server 2013 and SharePoint Server 2016.
Profile redirection works as follows:
Profiles for all hybrid users are in Office 365. Clicking a hybrid user's profile in SharePoint Server redirects you to their profile in Office 365 (even if you're not a hybrid user yourself).
If you choose to use a SharePoint audience when you configure hybrid sites features, non-hybrid users (those not in the audience) retain their SharePoint Server profiles, and they also have profiles in Office 365 if they are licensed Office 365 users.
Moving profile data to Office 365
Many enterprises have business requirements to replicate custom attributes to the SharePoint Online user profile service. Some user attributes are synchronized from Active Directory Domain Services to Azure Active Directory. You can select which attributes are replicated from Active Directory Directory Services to Azure Active Directory. However, a standard set of attributes are replicated from Azure Active Directory to the SharePoint Online user profile store in Office 365. This set of attributes cannot be customized like it can in SharePoint Server.
For custom attributes that are not located in Active Directory Directory Services, a user profile bulk API is available. There is also a synchronization tool that uses the bulk update API.
The process works like this:
You compile the needed profile data from SharePoint Server, your line-of-business system, or any other external system, into a JSON formatted file.
The tool uploads the JSON file to Office 365 and queues an import process.
A timer job running in SharePoint Online checks for queued import requests and performs the import operation based on the API calls and information in the provided file.
For more information about the bulk update API, see Introducing Bulk UPA Custom Profile Properties Update API for SharePoint Online.
Working with Delve in SharePoint hybrid deployments
If Office Delve is part of your Office 365 tenant, user profiles will be integrated with Delve, otherwise you'll have standard Office 365 profiles. If you haven't used Delve before, you'll want to learn more about it and how to administer it. Delve user profiles contain the same properties as SharePoint Online profiles and can be imported in the same manner, as described above in Moving profile data to Office 365.
Setting up hybrid profiles
Hybrid profiles is part of several hybrid feature bundles for SharePoint Server. For details, see Hybrid sites features and OneDrive for Business.