Google continues to change targeting settings in Demand Gen advertising campaigns. This time, the changes affect Lookalike audiences.
Previously, advertisers could limit ad impressions to users selected by Google based on an existing audience list. Now, the algorithm will be able to go beyond that audience and independently find new users.
At the same time, Google has decided to keep the option to opt out of automatic audience expansion. Search Engine Land reported this on October 12, citing the company's documentation.
What is changing for lookalike audiences
Demand Gen — is a type of Google Ads campaign for displaying ads on YouTube, Gmail, Google Discover and other Google ad placements.
Lookalike audiences are among the targeting options used to find audiences in Demand Gen. Advertisers provide Google with an existing audience list, and the algorithm uses it to find new people with similar characteristics.
When creating a Lookalike audience, advertisers also choose how broad the reach should be. There are three settings for this.
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Narrow. Google selects the most similar users within 2.5% of the audience in the selected GEO;
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Balanced. Reach increases to 5%, so the audience includes more people, including those less similar to the original audience list;
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Broad. The broadest option, allowing Google to reach up to 10% of users in the selected GEO.
Previously, the selected percentage served as a limit for ad impressions. For example, with Narrow at 2.5%, Google had to stay within the defined lookalike audience.
After the update, Lookalike audiences will work in Audience Suggestions mode by default. The original audience list and selected percentage will remain, but they will no longer serve as strict targeting limits.
According to Google, this will allow the algorithm to find more potential customers and better optimize campaigns for conversions or a specified CPA.
Google will allow advertisers to opt out of audience expansion
The transition to the new system began back in spring 2026. However, Google has decided to preserve the option for advertisers to use Lookalike audiences under the previous rules.
For this purpose, the Targeting Constraint mode is available. When enabled, the selected lookalike audience once again becomes a limit for ad impressions.
In other words, if a media buyer creates a Lookalike audience based on a specific audience list and selects 2.5% reach, Google will not be able to independently expand ad delivery beyond that audience.
Advertisers can currently opt out of the update through a special Google form. After submitting a request, the company promises to apply the change within three days. Later, the corresponding settings should appear directly in the Google Ads interface.
If no changes are made, Lookalike audiences will gradually transition to the new system.
What this means for affiliate marketers
The update primarily affects media buyers who use their own audience lists to find similar users.
If a setup is already generating conversions at the desired cost with a narrow Lookalike audience, it is worth monitoring CPA after the update. Audience expansion may cause it to change, even if all other campaign settings remain the same.
If expansion is not needed, the previous restrictions can be restored by opting out of the update. In other cases, no changes are necessary.
