Lookalike audience segments

You can target audiences that are similar and share characteristics with others using Lookalike segments. Lookalike segments are built from first-party data, for example, a list of customers who have purchased specific products or used specific services.

You can learn more about Lookalike segments in the Google Ads Help Center.

Create the user list

Creating a Lookalike user list follows the same process of creating other UserList types. Lookalike user lists are created with the UserListService by setting the lookalike_user_list field with a LookalikeUserListInfo object.

LookalikeUserListInfo is created based on existing audience segments. When creating a Lookalike segment, you need to pass these existing audience segments in the seed_user_list_ids field.


  1. The sum of all seed lists must include a minimum of 1,000 active matched people.

  2. Set the expansion_level to NARROW, BALANCED, or BROAD to configure the size of the lookalike segment. Find details on each level in the Help Center.

Best practices

It could take some time after creating your new campaign before you can effectively use your Lookalike segment. As a best practice, we recommend creating your campaign and Lookalike segment two to three days in advance to help ensure that it's ready when you want to start serving ads.

Lookalike segments refresh automatically every 1-2 days based on your available customer data. If the minimum count of active users is not met, it could take up to 3 days for your Lookalike segment to reflect the failed seed list requirement and stop targeting potential customers. Check that your user list has enough users by querying for user_list.size_range_for_display and user_list.size_range_for_search.

Code example

The process of creating and targeting a Lookalike user list is similar to creating a rule_based_user_list. You can find example code to create and target a rule_based_user_list, which can be adapted to a Lookalike user list, in Visitors to your website.

Review list performance

In order to collect performance data for your audience segments, issue a search request against the ad_group_audience_view or the campaign_audience_view resource. For example, you might look at the conversions or cost_per_conversion to determine if targeting the audience segment is actually leading to more conversions, then adjust your bid modifiers accordingly.

FROM ad_group_audience_view