For years, splitting campaigns by device was a no-brainer for Viajala. Google’s Smart Bidding just couldn’t be trusted to handle mobile and desktop traffic in the same campaign, where desktop traffic's value was so much higher. It would consistently over- or underbid mobile, tanking performance unless we intervened with device-specific splits and dedicated tROAS portfolios.

But Google claims Smart Bidding has come a long way. So we decided to put that claim to the test.

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The Setup: Device-Specific Campaigns for Control

Before the test, we had a tried-and-true setup:

• Separate campaigns for mobile and desktop.
• Separate tROAS portfolios for each device type.
  
  

Why? Because Smart Bidding simply wasn’t reliable enough at the time. Mixing mobile and desktop in a single campaign often led to inconsistent bidding behavior, particularly on mobile. By keeping campaigns separate, we maintained greater control and helped ensure more predictable performance.

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The Hypothesis: Maybe Smart Bidding Has Grown Up

With recent improvements to Smart Bidding, we started to wonder: is all that complexity still necessary? Our hypothesis was straightforward:

If we merge mobile and desktop campaigns, Smart Bidding will optimize across both devices effectively, and maybe even perform better thanks to more consolidated data.

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How We Ran the Test

We chose two medium-sized campaigns from two different Google Ads accounts. Here's what we did:

1. Enabled mobile targeting in the desktop campaign.
2. Kept the mobile campaign running temporarily, just to catch any weird behavior.
3. Monitored mobile traffic flowing into the desktop campaign (it started within a day).
4. Once we confirmed the traffic shift, we paused the mobile campaign.
5. Watch budgets closely to limit exposure in case of negative impact.

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What Happened Next Surprised Us

There was no “learning phase” dip. No volatility. No ramp-up period.

Smart Bidding picked up mobile traffic immediately, and bid correctly from day one.

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That’s worth repeating: bidding was on point right out of the gate.

We didn’t just avoid a performance hit. Performance stayed stable. Reliable. Controlled.

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The Result: One Campaign to Rule Them All

The test confirmed what we hoped: splitting by device is no longer necessary. Smart Bidding now handles mobile and desktop traffic well in a single campaign.

We’ve since merged device-specific campaigns across all accounts, with zero regrets,  and zero drop in performance.

But here’s the twist...

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What We Didn’t See: A Traffic Boost

Part of our theory was that combining device traffic into one campaign would give Smart Bidding more conversion data, and that this, in turn, would help it bid more aggressively and unlock more profitable traffic.

That didn’t happen.

While bidding was solid and performance held, we didn’t observe any meaningful lift in traffic or volume. More data didn’t automatically translate to more scale.

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Key Takeaways

• You can safely merge mobile and desktop campaigns. Smart Bidding is finally capable of handling device-level bidding without manual splits.
  
  
• Don’t expect a magic uplift in traffic. Consolidating data helps with consistency, but it won’t necessarily unlock new scale.
  
  
• Keep a close eye on budgets during transition. Just in case performance swings unexpectedly (though in our case, it didn’t).
  
  

Bottom line: if you're still splitting campaigns by device in 2025, it's time to reconsider. Smart Bidding has matured, and simplifying your structure could reduce overhead without sacrificing performance.

Want help figuring out whether it's time to consolidate your campaigns? Get in touch with us.

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