All users are identified using a unique attribute such as email, mobile number, custom id, etc. These identifiers are generated when users provide information about themselves, such as when they log in with an email id, mobile number, or username. In addition, users may visit your app or website using multiple devices, and until the user logs in, we will not know if this user is new or existing.

MoEngage classifies users as:

• Anonymous User - A user who hasn’t been identified yet by the website or the app. This could be a user who has been using the app/website but hasn’t logged in or a completely new user who hasn’t signed up.
• Registered User - A user who has signed up or logged in to your website or app.

Terms to Know

• MoEngage ID - MoEngage creates a unique identifier as soon as a user visits your website or app to recognize a user, which is a non-changeable value.
• ID - When a user registers on your app or website (by providing a form of email, phone number, or user id), we recommend you generate a unique identifier for that profile and pass it to MoEngage as an ID. This ID lets you recognize the user across multiple devices and platforms, thus providing a 360° view. This ensures that information about the user is captured correctly even if they uninstall and reinstall the app.

MoEngage ID and ID - Relationship

• New User - When a user opens or visits the app for the first time, neither the brand nor MoEngage has any information about them. MoEngage assigns a MoEngageID to this user and creates an anonymous profile for them. MoEngage records all actions that the user performs.
• Sign-up -If the user proceeds to sign up, they become a registered user or an identified user. The brand assigns a unique identifier for each user called ID. This information is passed to MoEngage, and this user is now considered a registered user in the MoEngage system.
• Registered user who hasn’t signed in initially - If the user has an account (has a MoEngage ID and an ID) but signs in after performing a series of events, a new MoEngage ID would have been created for them as they hadn’t signed in initially. Once they sign in,  the user profile created earlier with a new MoEngage ID is merged with this existing MoEngage ID.

User Merging Scenarios

MoEngage enables you to have a single user ID for all your users, even if they are using different devices. The only condition for merging users in MoEngage is that the user has to be signed in on the device. When a user visits your website or app, MoEngage merges the anonymous user profile with the registered user profile once they log in to the system.

Scenario 1: When the user visits your website or app for the first time on a device (Device 1), then they are user called an anonymous user, and a MoEngageID is set as MoEID-1 for that user.
If the user logs in, this user is an identified user and an ID called U-1 is set for the user. All events on this device, until the user logs out or uninstalls, are attributed to MoEID-1.

Scenario 2: If the same user visits the website/app from another device (Device 2), then this user is still an anonymous user since MoEngage does not know the identity of this user, and a new MoEngageID MoEID2 is created for the user. If the user logs in, the website or app notifies MoEngage that the user ID is U-1. Now, the anonymous user is merged with the already existing registered user.

Merging Impact on User Attributes

A retained user is a previously identified/registered user. The anonymous user gets merged into the identified/registered user.

Here's what happens during user merging:

• The 'First Seen' attribute of the retained user is kept.
• The values of LTV, No. of Conversion, and No. of Sessions attributes get added from both profiles and are stored in the retained profile.
• The attributes present in the retained user will be kept as is and will not be modified.
• The attributes that are not present in the retained user and present in the anonymous user will be copied to the retained user.
• Push Reachability calculation is done based on the overall devices.
• If the 'Email (Standard)' attribute is copied to the retained user, email suppression attributes (Hard Bounce, Spam, Unsubscribed) are also copied.

Merging Impact on Events

All the events occurring after the user merge are attributed to the identified/registered user. All events performed before are also attributed to the identified/registered user.