Google Ads Smart Bidding relies on machine learning to optimize campaigns automatically. However, the quality of the optimization depends heavily on the conversion signals provided to Google's algorithm.
Many advertisers experience poor Smart Bidding performance because they allow too many conversion actions—such as page views, button clicks, newsletter signups, or low-value interactions—to influence bidding decisions.
The solution is creating a clear separation between primary conversions and secondary conversions.
Key takeaways:
- Primary conversions should drive Smart Bidding decisions while secondary ones are for measurement only
- Poor conversion signals cause Google's AI to optimize for quantity instead of quality
- Separating primary vs secondary conversions improves ROAS and lead quality
- Clean conversion structure helps Maximize Conversions, tCPA, and tROAS strategies
- Always allow learning period after updating conversion settings
Core Concept: Primary vs Secondary Conversion Framework
Google Ads does not simply optimize for more conversions. It optimizes based on the conversion actions marked as important signals.
A conversion framework helps advertisers tell Google's AI:
- Which actions directly generate business value
- Which actions are useful for measurement only
- Which signals should influence automated bidding decisions
Primary Conversion Actions
Primary conversions are the actions that Google Ads Smart Bidding should optimize toward. These represent valuable business outcomes.
Examples:
Purchase completed — Direct revenue generation
Qualified lead submission — Sales opportunity creation
Phone call from high-intent customer — Offline sales potential
Booking confirmation — Revenue-generating customer action
Demo request — High-value B2B lead
Primary conversions should be included in the "Conversions" column, guide Smart Bidding algorithms, have accurate tracking values, and reflect real business goals.
Secondary Conversion Actions
Secondary conversions are useful measurement signals but should not control bidding decisions.
Examples:
Page views — Understand content engagement
Add-to-cart — Analyze buying behavior
Button clicks — Measure user interaction
Newsletter signup — Build audience lists
Video views — Measure awareness
These actions should remain available for reporting but be excluded from bidding optimization.
Why Smart Bidding Performance Declines
Google Ads AI learns from conversion data. If advertisers provide poor-quality signals, the algorithm may optimize toward actions that increase conversion numbers but decrease business value.
Too Many Conversion Actions
A company wanting leads but including blog visits, PDF downloads, and time-on-page may cause the system to chase cheaper, low-value actions.
Optimizing for Quantity Instead of Quality
A campaign with 200 low-quality conversions often performs worse than one with 20 high-quality leads.
Recommended Google Ads Conversion Structure
Sales purchase — Primary → Optimize bidding
Qualified lead — Primary → Optimize bidding
Phone enquiry — Primary → Optimize bidding
Add to cart — Secondary → Analyze funnel
Newsletter signup — Secondary → Audience building
Page engagement — Secondary → Reporting
How This Improves Smart Bidding
A cleaner conversion framework helps Google Ads AI:
- Understand your actual business goals
- Find higher-quality users
- Improve bidding decisions
- Reduce wasted ad spend
- Increase return on ad spend (ROAS)
This framework improves performance for Maximize Conversions, Maximize Conversion Value, Target CPA, Target ROAS, and Performance Max campaigns.
Implementation Checklist
Conversion Tracking Audit
- Check all conversion actions are correctly installed
- Remove duplicates
- Assign accurate values where possible
Conversion Classification
Mark revenue-generating and sales-qualified actions as Primary.
Mark engagement and supporting metrics as Secondary.
Monitor Performance
After changes, track conversion volume, quality, cost per acquisition, ROAS, and lead quality. Allow sufficient learning time.
Frequently Asked Questions
What is the difference between primary and secondary conversions in Google Ads?
Primary conversions directly influence Smart Bidding and represent real business outcomes. Secondary conversions are for reporting and analysis only.
Will changing conversion settings affect my campaigns immediately?
Google Ads needs a learning period (usually 7–14 days) after major changes to conversion actions. Avoid frequent changes.
Should I assign values to all conversions?
Yes, especially for primary conversions. This helps Target ROAS and Maximize Conversion Value strategies perform better.
Conclusion
Many advertisers struggle with Smart Bidding because they feed poor-quality signals to Google's machine learning. By clearly separating primary business conversions from secondary engagement metrics, you give the AI the clarity it needs to optimize toward outcomes that actually matter to your business.
Need help auditing your Google Ads conversion tracking and implementing a primary vs secondary framework? Contact our PPC team for a Smart Bidding optimization review.