Liam Walsh
Liam is a Co-Director at Intelligency and heads up the agency's Digital Intelligence & Paid Social activity. Over the last decade, he has worked with brands from the world of sports such as Premier League clubs to entertainment such as Channel 4 and Disney.
For months, Google said advertisers couldn’t block certain websites or placements in Performance Max (PMax) campaigns using automated tools (API). However, new research proved otherwise, and Google has now admitted that these controls do work—giving advertisers more control than they previously thought. A Performance Max (PMax) campaign is an automated ad campaign in Google Ads that uses AI and machine learning to show ads across multiple platforms, including Google Search, YouTube, Display Network, Gmail, Discover, and Maps. Instead of manually selecting where ads appear, advertisers provide creative assets, a budget, and a goal (such as sales or leads), and Google’s AI optimizes the campaign for the best results. PMax is popular because it saves time, expands reach, and focuses on driving conversions. However, many advertisers find it lacks control and transparency, making it difficult to see where ads are placed or make manual adjustments.
A Simple Experiment Proved Google Was Wrong
A marketing tech company, Optmyzr, tested Google’s claims by running an experiment from December 30 to January 21. They found that ads completely avoided the blocked placements when using API exclusions. This method also worked faster and more efficiently than manually blocking placements through Google’s interface.
Google’s Misinformation Misled Advertisers
For months, Google’s official documentation and customer support said API-based blocking wasn’t possible. This misinformation meant advertisers wasted time using less efficient methods—or didn’t block bad placements at all. After the experiment proved otherwise, Google quietly updated its guidance.
What This Means for Advertisers
Now that Google has confirmed these controls work, advertisers can prevent their ads from appearing on irrelevant or low-quality sites more easily. This discovery also shows that companies shouldn’t blindly trust what ad platforms say—they should test things for themselves.
Lesson Learned: Always Question Tech Platforms
This case is a reminder that big tech platforms don’t always provide accurate information about their tools. Advertisers—and anyone using digital platforms—should question official claims, test features themselves, and look for hidden options that could improve their results.
