Google Ads Smart Bidding: How to Use Primary vs Secondary Conversions for Better Results
What Is Google Ads Smart Bidding?
Google Ads Smart Bidding is an automated bidding strategy that leverages machine learning to make bids that are optimised for likelihood of conversion.
Smart Bidding analyses hundreds of signals, such as:
- User behavior
- Device type
- Geographic location
- Time of day
- Audience characteristics
- Search intent
- Historical conversion data
It learns from conversion actions over time and adapts its bid accordingly.
Google says that you need to have accurate conversion tracking in place for Smart Bidding to make effective decisions for optimization. Bad conversion data leads to the learning of inappropriate behaviours, resulting in sub-optimal business results.
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Why Smart Bidding Often Fails
Many advertisers think that Smart Bidding isn't working when their campaigns bring in lots of conversions and fewer sales.
The real trouble is typically on the conversion architecture.
Suppose the following are all conversions:
- Button clicks
- Form interactions
- Add-to-cart events
- Checkout starts
- Product purchases
If everything is treated the same, Google will get mixed signals.
It begins optimizing for whatever action is the easiest to make, not for those who make money for you. It optimizes for what it can optimise for, which is the action that's easiest, not for those who make money for you.
The Result
- Conversion rates seem high
- ROAS looks impressive
- Reports seem successful
- Real business growth has been slow
This is one of the most prevalent reasons why Smart Bidding fails to perform as well.
Understanding Primary vs Secondary Conversions
The Primary vs Secondary Conversion Framework is a tool that assists advertisers in distinguishing between optimization signals and reporting signals.
What are Primary Conversions?
Primary conversions are the ones that have the most direct impact on Google's bidding process.
These actions should be actual business effects including:
- Purchases
- Qualified leads
- Consultation bookings
- Demo requests
- Revenue-generating phone calls
These actions are used to train its machine learning models.
What are Secondary Conversions?
Secondary conversions are not a direct measure of bidding optimisation.
Examples include:
- Add to Cart
- Begin Checkout
- Pricing Page Views
- Product Video Views
- Account Registrations
- Contact Page Visits
These actions are used to track users without impacting on how the bids are made.
How Google's Algorithm Uses Conversion Signals
Google's Smart Bidding algorithm processes conversion signals to determine which auctions to enter and how much to bid. The quality and structure of these signals directly determine campaign performance.
| Signal Type | How Google Uses It | Impact on Bidding |
|---|---|---|
| Primary Conversions | Direct optimization target for machine learning | High — directly influences bid amounts and auction participation |
| Secondary Conversions | Tracked for reporting and funnel analysis only | None — not used for bidding optimization unless in custom goals |
| Micro Conversions | User engagement signals (scroll, clicks, time) | Low — useful for audience building but not bidding |
| Offline Conversions | CRM data imported back to Google Ads | High — when set as primary, closes the loop between marketing and sales |
Key Insight: Google still recommends at least 30 primary conversions per month for Smart Bidding to function optimally. Journey Aware Bidding, currently in testing, expands this by learning from multiple touchpoints while keeping one clear primary goal.
Common Conversion Tracking Mistakes
Here are some of the most frequent conversion tracking errors that people make:
Tracking Too Many Primary Conversions
The most frequent error made is to register all significant interactions as primary conversions.
This generates signal pollution and makes it hard to accurately optimize.
Using Micro Conversions as Revenue Signals
Micro conversions can also be useful for reporting but don't necessarily have an immediate impact on revenue.
Examples include:
- Scroll depth
- Button clicks
- Page engagement
- Time on site
Such actions should not be objectives to work toward most of the time.
Ignoring Custom Goals
Custom goals can have the opposite effect to conversion settings and be unintentional conversion signals.
This problem can be avoided by conducting regular audits.
Forgetting GA4 Import Settings
Conversions that are imported into Google Analytics 4 will sometimes fall into secondary status.
Some advertisers do not even know about this setting and unknowingly disconnect Smart Bidding from their own business goals.
The Benefits of a Primary vs Secondary Framework
Implementing a clear Primary vs Secondary conversion structure delivers measurable improvements across campaign performance:
Key Benefits
- Signal Clarity: Google receives unambiguous optimization targets, reducing algorithm confusion.
- Improved ROAS: Bidding focuses on revenue-generating actions rather than easy micro-conversions.
- Better Lead Quality: Smart Bidding learns to find users who complete high-value actions.
- Accurate Reporting: Primary conversions reflect true business outcomes in main reporting columns.
- Funnel Visibility: Secondary conversions still track user journey stages for analysis.
| Feature | Primary Conversion Actions | Secondary Conversion Actions |
|---|---|---|
| Main Purpose | Used for campaign optimization and bidding | Used for tracking additional insights |
| Reports Column | Shown in "Conversions" and "Conv. value" columns | Shown only in the "All conversions" column |
| Used in Smart Bidding | Yes (e.g., Maximize Conversions, Target CPA) | No (unless part of a custom goal) |
| Helps Measure Campaign Success | Directly aligns with key business goals | Tracks supporting user actions |
| Impact on Budget Allocation | Helps Google Ads focus spend on what matters most | Doesn't influence ad spend optimization |
| Ideal Use Case | When you want to drive conversions and ROI | When you want to gather more detailed insights |
Setting Up Primary and Secondary Conversions
Step 1: Identify Your Revenue Goal
Choose one primary action that directly aligns with revenue.
Examples:
- Purchase
- Qualified Lead
- Booked Consultation
Step 2: Separate Funnel Actions
Move all supporting actions into secondary status.
Examples:
- Product Views
- Add to Cart
- Checkout Started
- Pricing Page Visits
Step 3: Audit Custom Goals
Review all campaign-level goals to ensure secondary actions are not accidentally being used for bidding.
Step 4: Verify GA4 Imports
Confirm imported conversions are properly classified after synchronization.
Step 5: Monitor Learning Periods
Allow Google sufficient time to adjust after making structural changes.
Most campaigns require:
- 7 to 14 days for standard learning
- Up to 30 days after major conversion cleanup
Pro Tip: Start New Conversions as Secondary
When you create a new offline conversion action, set it to Secondary, not Primary. The default is Primary, and accepting the default is the most common mistake we see.
A Primary conversion enters your main reporting columns and, more importantly, enters your bidding. If you flip a brand-new conversion straight to Primary, Smart Bidding starts optimising against a signal it has no history for, and delivery gets unstable while it works it out.
Special Cases Every PPC Manager Should Know
Phone Call Conversions
Phone calls require careful evaluation.
- If calls regularly generate sales: Mark as Primary
- If calls are mostly informational: Mark as Secondary
Review actual call recordings whenever possible.
Low-Volume Accounts
Businesses with limited conversions may struggle to provide enough data for Smart Bidding.
In these situations:
- Keep primary goals strict.
- Use meaningful secondary conversions for funnel analysis.
Performance Max Campaigns
Performance Max campaigns are especially sensitive to conversion quality.
Poor conversion architecture can quickly lead Google's automation toward low-quality traffic sources.
Offline Conversions & CRM Integration
For B2B and high-consideration funnels, Enhanced Conversions for Leads is essential. This feature allows you to connect offline outcomes — such as lead stage updates, qualified leads, or closed deals — back to the original ad interaction.
By securely sending hashed lead data to Google, you close the loop between marketing and sales, Smart Bidding can optimize for quality not just volume, and ROI attribution becomes far more accurate.
When Should You Promote a Secondary Conversion?
In most cases, secondary conversions should remain secondary.
Legitimate exceptions include:
When to Promote
- Qualified Phone Calls: If business analysis confirms strong sales intent.
- Revenue-Based Offline Conversions: When CRM data demonstrates direct revenue impact.
- Improved Lead Qualification: When a business shifts from basic leads to qualified leads as its primary KPI.
Important Note
When you do move an offline conversion to Primary, change your bidding targets at the same time. Suppose you run a Target CPA of $150 optimising toward online leads. You generate 36 leads a week and 10 of them become SQLs — a 28% rate. If you switch the bidding goal to SQLs and leave the target at $150, you are asking Google to produce an SQL for the price of a lead. It cannot, so it throttles delivery to protect the target it can no longer hit. The correct target is roughly the old one divided by the conversion rate.
Outside these situations, promotion is rarely recommended.
Smart Bidding Audit Checklist
Before launching any bidding experiment, verify:
- One primary goal per campaign objective
- Revenue-focused primary conversions
- Micro conversions marked secondary
- GA4 imports reviewed
- Phone call quality assessed
- Custom goals audited
- Reporting columns verified
- Funnel tracking maintained
- Learning period respected
- Conversion architecture documented
Best Practices for 2026 and Beyond
As automation expands, the role of PPC professionals continues to evolve.
Google increasingly automates:
- Bidding
- Audience targeting
- Creative optimization
However, conversion architecture remains a human responsibility.
The Future Advantage
The future advantage belongs to marketers who can:
- Define meaningful business outcomes
- Structure conversion frameworks correctly
- Align machine learning with revenue goals
The algorithm can optimize performance, but only after receiving the right instructions.
2026 Trend: Journey Aware Bidding (JAB) is currently in closed testing. Instead of focusing exclusively on the final conversion, the algorithm will learn from the entire customer journey. Intermediate actions — such as downloading a guide, participating in a webinar, or booking a demo — can be used as signals to assess which clicks have the greatest probability of creating value in the long term.
Conclusion
The effectiveness of Google Ads Smart Bidding depends on the quality of the signals it takes.
Using a Primary vs Secondary Conversion Framework, advertisers can remove signal noise, increase the accuracy of machine learning, and optimize their campaigns more in line with real business goals.
Instead of optimizing for clicks, form opens, or other low-intent behaviors, you can optimize for outcomes that have a direct impact on revenue and growth.
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"Advertising is only evil when it advertises evil things."
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Frequently Asked Questions
1. What is Primary and Secondary conversions in Google Ads?
Primary conversions are used for Smart Bidding optimization, secondary conversions are not used for Smart Bidding optimization but for reporting or analysis.
2. Is the primary conversion Add to Cart?
No, in most cases Add to Cart is a micro conversion, and should be a secondary conversion.
3. What is the time that it takes after the conversion changes for Smart Bidding?
Google takes 7-14 days to recognize major conversion changes, and up to 30 days for bigger changes.
4. Do the secondary conversions affect bidding?
Google's official documentation says that secondary conversions are not counted towards Smart Bidding optimization. But, they do give some useful reporting information.
5. Which is the best conversion one can use as the primary conversion?
The primary conversion that is most closely related to revenue generation is the best primary conversion, whether it's purchases, qualified leads or booked consultations.
6. How many primary conversions should I have?
Most accounts should have 1–3 primary conversion actions — focused on high-value outcomes like purchases, qualified leads, or booked calls. Having too many primary conversions sends conflicting signals to Smart Bidding and dilutes optimization.
7. Should I use GA4 imported events as primary conversions?
No. GA4-imported key events have longer reporting delays and use a different attribution model than native Google Ads conversion tags. For primary bidding actions, purpose-built Google Ads conversion tags provide cleaner, faster, more accurate signals for Smart Bidding to work with.
