How to Avoid Duplicate Lookalike Audiences on Google
Important Update: Changes Coming to Google Ads API for Lookalike User Lists in 2026
A crucial adjustment is on the horizon within the Google Ads API landscape that will have a significant impact on how advertisers and developers craft Lookalike user lists, especially for those spearheading Demand Gen campaigns.
What's Happening
Google is set to implement a uniqueness validation on Lookalike user lists, thwarting the creation of duplicates that are based on the same seed lists, expansion level, and country targeting. From April 30 onwards, any attempt to generate a duplicate list will trigger an API error message.
Significance of this Change
For teams leveraging automated scripts or third-party tools to algorithmically produce audience lists, overlooking this adjustment could potentially disrupt campaign workflows if integrations are not promptly revised.
Actions to Take
- Conduct an audit of existing Lookalike lists and consider reusing those that align with your intended setup instead of initiating new ones.
- Revamp your API error handling mechanism to identify and handle the new
DUPLICATE_LOOKALIKEerror code for version 24 and above, orRESOURCE_ALREADY_EXISTSfor earlier versions.
Key Takeaway
This alteration is essentially a maintenance measure geared towards ensuring the stability of Google’s systems. Nevertheless, it is crucial to adhere to the April 30 deadline. Developers and agencies engaged in programmatically managing campaigns are urged to treat this as a technical task to be addressed before the end of April.
Further Information
For a more in-depth understanding of the upcoming modifications concerning Lookalike user lists in the Google Ads API, commencing on April 30, 2026, visit Upcoming changes to Lookalike user lists in the Google Ads API, starting April 30, 2026
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