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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.
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.
Requirements
The sum of all seed lists must include a minimum of 1,000 active matched
people.
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.
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Missing the information I need","missingTheInformationINeed","thumb-down"],["Too complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-09-03 UTC."],[[["\u003cp\u003eLookalike segments allow you to target potential customers similar to your existing customer base using first-party data for Demand Gen campaigns.\u003c/p\u003e\n"],["\u003cp\u003eCreating Lookalike segments involves providing seed user lists with a minimum of 1,000 active matched people and specifying an expansion level (Narrow, Balanced, or Broad).\u003c/p\u003e\n"],["\u003cp\u003eFor optimal performance, it is recommended to create your campaign and Lookalike segment 2-3 days in advance to allow for data processing.\u003c/p\u003e\n"],["\u003cp\u003eLookalike segments refresh automatically, but require a minimum active user count, and performance can be monitored using ad_group_audience_view or campaign_audience_view resources.\u003c/p\u003e\n"],["\u003cp\u003eYou can find additional information and expansion level details in the Google Ads Help Center.\u003c/p\u003e\n"]]],[],null,["# Lookalike audience segments\n\nYou can target audiences that are similar and share characteristics with others\nusing Lookalike segments. Lookalike segments are built from first-party data,\nfor example, a list of customers who have purchased specific products or used\nspecific services.\n| **Important:** Lookalike segments are only available for Demand Gen campaigns.\n\nYou can learn more about Lookalike segments in the [Google Ads Help\nCenter](//support.google.com/google-ads/answer/13541369).\n\nCreate the user list\n--------------------\n\nCreating a Lookalike user list follows the same process of creating other\n[`UserList`](/google-ads/api/reference/rpc/v21/UserList) types. Lookalike user lists are created\nwith the [`UserListService`](/google-ads/api/reference/rpc/v21/UserListService) by setting the\n[`lookalike_user_list`](/google-ads/api/reference/rpc/v21/UserList#lookalike_user_list) field with a\n[`LookalikeUserListInfo`](/google-ads/api/reference/rpc/v21/LookalikeUserListInfo) object.\n\n[`LookalikeUserListInfo`](/google-ads/api/reference/rpc/v21/LookalikeUserListInfo) is created based\non existing audience segments. When creating a Lookalike segment, you need to\npass these existing audience segments in the `seed_user_list_ids` field.\n\n### Requirements\n\n1. The sum of all seed lists must include a minimum of 1,000 active matched\n people.\n\n2. Set the [`expansion_level`](/google-ads/api/reference/rpc/v21/LookalikeExpansionLevelEnum) to\n `NARROW`, `BALANCED`, or `BROAD` to configure the size of the lookalike\n segment. Find details on each level in the [Help\n Center](//support.google.com/google-ads/answer/13541369).\n\n### Best practices\n\nIt could take some time after creating your new campaign before you can\neffectively use your Lookalike segment. As a best practice, we recommend\ncreating your campaign and Lookalike segment two to three days in advance to\nhelp ensure that it's ready when you want to start serving ads.\n\nLookalike segments refresh automatically every 1-2 days based on your available\ncustomer data. If the minimum count of active users is not met, it could take up\nto 3 days for your Lookalike segment to reflect the failed seed list requirement\nand stop targeting potential customers. Check that your user list has enough\nusers by querying for\n[`user_list.size_range_for_display`](/google-ads/api/fields/v21/user_list#user_list.size_range_for_display)\nand\n[`user_list.size_range_for_search`](/google-ads/api/fields/v21/user_list#user_list.size_range_for_search).\n\n### Code example\n\nThe process of creating and targeting a Lookalike user list is similar to\ncreating a `rule_based_user_list`. You can find example code to create and\ntarget a `rule_based_user_list`, which can be adapted to a Lookalike user list,\nin [Visitors to your\nwebsite](/google-ads/api/docs/remarketing/audience-segments/website-visitors).\n\nReview list performance\n-----------------------\n\nIn order to collect performance data for your audience segments, issue a search\nrequest against the [`ad_group_audience_view`](/google-ads/api/fields/v21/ad_group_audience_view)\nor the [`campaign_audience_view`](/google-ads/api/fields/v21/campaign_audience_view) resource.\nFor example, you might look at the `conversions` or `cost_per_conversion` to\ndetermine if targeting the audience segment is actually leading to more\nconversions, then adjust your bid modifiers accordingly. \n\n SELECT\n ad_group_criterion.criterion_id,\n metrics.conversions,\n metrics.cost_per_conversion\n FROM ad_group_audience_view"]]