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Navigate Google’s New Rule on Duplicate Lookalike Lists

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Written by

shivamcrushpressai

in

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I recently discovered an important update from Google affecting how I run Demand Gen campaigns using Lookalike user lists. Starting April 30, Google will block creating duplicate Lookalike lists via the Google Ads API and return an error code for any breaches.

This update might seem quiet, but its implications are significant, especially for those of us utilizing automated systems or third-party tools. Google is now enforcing a uniqueness check to prevent duplicates that have identical seed lists, expansion level, and country targeting.

Why do I care about this change? An unaddressed error could disrupt the workflow of my campaigns if I don’t update my integrations in time.

Here’s what I plan to do:

  • Audit my current Lookalike lists and reuse those that already align with my goals instead of creating new ones.
  • Update my API error handling processes to catch the new DUPLICATE_LOOKALIKE error code in versions v24 and above, or RESOURCE_ALREADY_EXISTS in older versions.

The bottom line is, while this change is housekeeping, the deadline is firm. I need to ensure my campaigns are technically prepared before the end of April to maintain stability in Google’s systems.

If you’re interested in a deeper dive, I highly recommend checking out Google’s blog post detailing these changes: Upcoming changes to Lookalike user lists in the Google Ads API, starting April 30, 2026.

Inspired by this post on Search Engine Land.

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FAQs

What change is Google implementing regarding Lookalike lists?

Starting April 30, Google will block creating duplicate Lookalike lists via the Google Ads API and return an error code for any breaches. Google is enforcing a uniqueness check to prevent duplicates that have identical seed lists, expansion level, and country targeting.

Why is Google making this change?

Google is enforcing a uniqueness check to prevent duplicates that have identical seed lists, expansion level, and country targeting.

How could this change affect campaigns?

An unaddressed error could disrupt the workflow of campaigns if you don’t update your integrations in time.

What steps should I take to prepare?

Audit current Lookalike lists and reuse those that already align with your goals instead of creating new ones. Update API error handling to catch the new DUPLICATE_LOOKALIKE error code in versions v24 and above, or RESOURCE_ALREADY_EXISTS in older versions.

When is the deadline to be prepared?

Deadline is April 30, 2026. Prepare before the end of April to maintain stability.

Where can I read more about these changes?

Google’s blog post ‘Upcoming changes to Lookalike user lists in the Google Ads API, starting April 30, 2026’ provides a deeper dive. The link is included in the article.

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