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bid modifiers for device, location, and audience feel like control. in most cases they reduce performance.

here is why.

smart bidding is a real-time auction model. it evaluates hundreds of signals per impression: device, location, time of day, audience membership, query intent, ad history, landing page relevance. it adjusts the bid accordingly.

when you add a -30% device modifier for mobile, you're telling the algorithm: regardless of what your real-time signals show about this specific mobile user, bid 30% less. you're overriding a signal-aware system with a blanket rule.

the cases where modifiers are justified: your conversion tracking is broken on mobile (so the algorithm can't see mobile conversions). your business genuinely cannot serve mobile users. you have strong statistical evidence, not gut feeling, that one device or location converts at a meaningfully different rate.

the cases where modifiers hurt: you added them because mobile CPA looked high in a 30-day window. you added location modifiers based on low-volume data from one campaign. you have audience bid adjustments that conflict with the audiences your smart bidding is already optimizing for.

the check: go to any campaign with bid modifiers. look at the number of conversions per segment over 90 days. if any segment has fewer than 30-50 conversions in that window, your bid modifier is based on noise, not signal.

if you're on target CPA or target ROAS, the cleaner move is to remove modifiers and let the algorithm do its job with clean conversion data.

/conversion-audit reviews your modifier setup as part of the bidding health check: https://paidmedialab.com/pack

saku