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Who Should Choose this Strategy?

The Customer Merge strategy is useful for brands that meet the following criteria:
  • With a lot of anonymous users
  • With fewer known first-party identifiers and more anonymous or third-party identifiers
  • Has access to second-party data that they want to overlay
Note:Assume that multiple UCIDs were created due to delayed linkage information. In that case, whenever a new event comes in, there can be multiple UCIDs to consider. The profile with the first created UCID is retained as the master profile and the other matched profiles are merged to it.

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Pros

  • The Default ID Strategy is simple to configure
  • By default, the anonymous user behavior is unified with the known user profiles.

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Cons

  • Linkages based on low fidelity can lead to the unification of multiple user profiles into one profile due to the presence of common IDs. For example, a family using the same device and browser, share the browser identifiers like GA ID and this may lead to the merging of their profiles together.
  • As the linkages use all identifiers, this in particular is not ideal for one-on-one personalization use cases, wherein customers get referred directly to their identity. For example, sending email communication based on their purchase or past interaction.

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How does the Strategy Work?

The following steps summarise how this strategy works:
1
Upon receiving any ID, create a UCID tied to all the IDs present.
2
After creating the UCID, any data flowing in for the same user against any of the linked identifiers are identified with the same UCID.
A typical use case explaining this strategy is one in which you want to link all the customer’s actions to an anonymous user and their behaviours as a logged-in user. Refer to the table below for more examples.
Note:This strategy is also especially useful when dealing with a lot of anonymous data and third-party identifiers.

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Reconciliation

When a new event comes in, if multiple UCIDs were created as a result of delayed linkage information, then there could be multiple UCIDs to consider. In that case, Zeotap functions in the following way:
  1. The profile with the first created UCID is retained as the master profile and the other matched profiles are merged to it.
  2. All the other UCIDs are reconciled to the master UCID.
  3. All the corresponding profiles and events are merged into the master UCID.
Note:In this use case, there is no priority defined for the identifiers.
We are considering the following IDs to further explain the how Default ID strategy works:
  • User ID
  • Email
  • Cellphone
  • Maid
  • GA Client ID
Last modified on February 26, 2026