Upcoming changes to Lookalike user lists in the Google Ads API, starting April 30, 2026

Google Ads is committed to providing a reliable and efficient environment for all advertisers. To ensure that our systems remain stable and that resources are allocated fairly, we are introducing a uniqueness check for Lookalike user lists that prevents the creation of duplicate lists. These changes primarily impact Demand Gen campaigns and will begin to be enforced starting on April 30, 2026 .