Ginny Marvin, the Google Ads Liaison, addressed this concern on X. She explained that the limit is designed to provide advertisers with additional control while ensuring that PMax campaigns retain the flexibility necessary to achieve their goals. Google’s automated systems work best when they have room to optimize, and an excessive number of negative keywords could hinder campaign performance.

While the 100-keyword cap may seem restrictive, Google offers additional tools to help advertisers refine where their ads appear:

• Brand exclusions: Prevent ads from showing for specific brand-related searches.
• Account-level negative keywords: Set negative keywords across all campaigns to maintain consistency.
• Keyword prioritization: Ensure that high-priority keywords drive the right traffic to your campaigns.