Google's AI is powerful. It's also happy to spend your money on whatever it thinks might convert.
Without guardrails, automation chases cheap wins instead of business outcomes. Here are the settings that keep your campaigns on track.
Performance Max Guardrails
1. Brand Exclusions
PMax loves brand traffic — it converts cheaply and makes performance look great. But you're paying for clicks you'd get organically.
Setting: Campaign settings → Brand exclusions → Add your brand terms
This prevents PMax from cannibalizing your brand campaigns. If you want PMax to capture brand traffic, run it separately with proper attribution.
2. Negative Keywords (Finally)
PMax now supports up to 10,000 negative keywords per campaign. Use them.
Start with:
- •"jobs," "careers," "salary," "hiring"
- •"free," "cheap" (if premium brand)
- •Competitor names (unless intentionally conquesting)
- •Irrelevant categories for your business
Note: Negatives only apply to Search and Shopping inventory — not Display, YouTube, or Discovery.
3. URL Exclusions
PMax can send traffic to any URL on your site. That includes blog posts, about pages, and old landing pages you forgot existed.
Setting: Campaign settings → Final URL expansion → Exclude URLs
Create a list of URLs that shouldn't receive paid traffic.
4. Device Targeting (New in 2025)
PMax often sends 80-90% of traffic to mobile. For B2B or high-consideration products, that's often waste.
Setting: Campaign settings → Devices → Select which devices to include
Options: Computers, mobile phones, tablets, TV screens. Exclude what doesn't convert.
5. Placement Exclusions
Your PMax ads can appear on sketchy websites, kids' apps, and irrelevant YouTube channels.
Setting: Tools → Content suitability → Placement exclusions
Add domains and apps you don't want to appear on. Check placement reports monthly for new additions.
AI Max Guardrails
1. Don't Enable Without Broad Match Keywords
If you enable AI Max without broad match versions of your keywords, it treats your exact/phrase match keywords as if they were broad — and attributes conversions to AI Max that belong to your existing keywords.
Fix: Add broad match versions of all keywords before enabling AI Max. This gives clean reporting.
2. Separate Brand, Non-Brand, and Competitor Traffic
AI Max blurs the lines between these. Use negative keyword lists to enforce separation:
- •Brand terms as negatives in non-brand campaigns
- •Competitor terms managed in dedicated campaigns
- •Non-brand terms excluded from brand campaigns
3. Text Guidelines
AI Max can generate ad copy variations. Control it.
Setting: Campaign → AI Max → Text guidelines
Specify terms to avoid, required messaging, and tone restrictions.
Smart Bidding Guardrails
1. Bid Caps
tROAS and tCPA strategies will spend whatever it takes to hit targets. Set limits.
Setting: Bid strategy → Portfolio bid strategy → Set maximum CPC
This prevents runaway bids during auction spikes.
2. Seasonality Adjustments
Smart Bidding optimizes on historical patterns. During Black Friday, it sees high conversion rates and bids aggressively. When the sale ends, it takes weeks to recalibrate.
Setting: Tools → Bid strategies → Advanced controls → Seasonality adjustments
Tell the system when conversion rates will temporarily spike so it doesn't overlearn.
3. Data Exclusions
If tracking breaks (duplicate conversions, tag errors), Smart Bidding thinks performance improved and bids up.
Setting: Tools → Bid strategies → Advanced controls → Data exclusions
Exclude date ranges with bad data to prevent contaminated learning.
Account-Level Guardrails
1. Auto-Apply Recommendations: OFF
Google suggests "optimizations" that often prioritize spend over profitability.
Setting: Recommendations → Auto-apply → Disable
Review recommendations manually. Apply what makes sense.
2. Search Partners: Test Carefully
Search Partners can be valuable or wasteful depending on your business.
Setting: Campaign settings → Networks → Segment reporting by network
If Search Partners underperform, exclude them.
3. Display Network Expansion: Usually OFF
For Search campaigns, Display expansion sends traffic to Display inventory. Usually not what you want.
Setting: Campaign settings → Networks → Uncheck Display Network
The Minimum Guardrail Checklist
If you do nothing else:
- ☐Brand exclusions on PMax
- ☐Negative keyword lists (minimum 100 terms)
- ☐URL exclusions for non-converting pages
- ☐Placement exclusions reviewed monthly
- ☐Auto-apply recommendations disabled
- ☐Device targeting set intentionally
- ☐Data exclusions ready for tracking issues
The Bottom Line
Automation is the driver. You're the one setting the destination and the guardrails.
Without guardrails, Google's AI optimizes for its definition of success — which may not match yours. Every setting above exists because advertisers learned the hard way what happens when you trust the algorithm completely.
Trust, but verify. Automate, but constrain.
This week: Audit your PMax campaigns for brand exclusions and negative keywords. Those two settings alone can save 10-20% of wasted spend.
