Device bidding in Google Ads allows advertisers to adjust bids up or down for clicks on specific device types — mobile, desktop, and tablet. Device bid adjustments are percentage-based modifiers applied on top of the base bid. If mobile traffic converts at 60% of the desktop conversion rate, a -30% mobile bid adjustment ensures you pay proportionally less for mobile clicks. Device bid adjustments are most impactful for Search and Shopping campaigns; Performance Max and Smart Display handle device allocation automatically without adjustments.
Device conversion rate differences are significant for most businesses. B2B professional services campaigns typically see desktop conversions at two to three times the mobile rate — users research on mobile but fill out complex forms on desktop. Ecommerce businesses see narrowing mobile-desktop gaps as mobile checkout has improved, though desktop often still converts slightly better for high-value purchases. Healthcare and local service businesses see strong mobile conversion rates, particularly from call extensions.
Device bidding analysis and strategy
- Analyse by device before adjusting — check conversion rate, CPA, and conversion value by device in the Dimensions report
- Set adjustments proportional to performance difference — if mobile CPA is 50% higher than desktop, a -25% to -33% mobile adjustment is appropriate
- Consider call conversions separately — mobile users who call rather than fill forms may convert at high rates even if form-based mobile conversion rates are low
- Tablet bidding — tablets often behave more like desktop than mobile for conversion purposes; analyse separately
- Maximum adjustments — Google allows up to -90% to +900% adjustment; extreme adjustments should be data-supported
- Seasonal changes — mobile vs desktop balance shifts during peak periods; review device performance seasonally
- Smart Bidding interaction — if using Target CPA or Target ROAS, Smart Bidding already adjusts by device automatically; manual device adjustments layer on top
Only in specific circumstances where mobile clicks genuinely generate zero conversions and no contribution to the conversion path — extremely rare for most businesses. Excluding mobile (-100% bid adjustment) blocks all mobile traffic, including mobile users who research on mobile and convert on desktop (multi-device paths attributed to the desktop click). Reducing mobile bids significantly (-50% to -70%) while keeping some mobile presence is better than complete exclusion for most accounts.
Significantly. A desktop-optimised landing page with small fonts, complex forms, and slow loading on mobile will convert mobile traffic at very low rates — making mobile CPAs poor compared to desktop. Before applying aggressive negative bid adjustments to mobile, verify that the landing page is genuinely mobile-optimised: loads in under 2 seconds on 4G, has a thumb-friendly interface, and makes the primary conversion action (form or call) easy to complete on a small screen. Improving mobile landing pages often increases mobile conversion rates enough to make mobile traffic profitable without bid adjustments.