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What changed
From April 30, Google Ads will enforce a uniqueness check for Lookalike user lists to prevent duplicates in Demand Gen campaigns.
Duplicate Lookalike segments that were previously tolerated will be flagged or rejected.
This applies to all Demand Gen campaigns using Lookalike audience targeting.
What it means
If you have been running Demand Gen campaigns with multiple Lookalike segments built from similar seed lists, some of those audiences may fail validation after April 30. This is Google cleaning up audience overlap that was inflating reach numbers without improving performance. For Australian advertisers using Demand Gen for top-of-funnel prospecting, this means your audience targeting needs to be tighter and more intentional.
What to do
Review all Lookalike audiences in your Demand Gen campaigns before April 30
Remove or consolidate duplicate seed lists that target overlapping customer segments
Check for warnings in the Google Ads audience manager over the next week
Test consolidated audiences now so you have performance baselines before enforcement begins
Source: Google Ads Developer Blog (April 2026)
