Cross-device attribution is one of the core differences between AI Max and traditional keyword-based campaigns. The AI's bidding decisions draw on a user's complete device journey, not just the device where the final conversion occurred. Understanding how this works changes how you interpret AI Max performance data.
How AI Max Reads Cross-Device Signals
AI Max for Search and AI Max for Shopping operate on Google's logged-in identity graph — when a user is signed into Google across their phone, laptop, and tablet, Google can observe the same user's behavior across those devices. This isn't unique to AI Max, but AI Max's bidding system uses this cross-device view actively.
When the AI evaluates a bid in a search auction, it's not only looking at "this user just searched for X on their phone." It's looking at patterns like:
- "This user searched for X on mobile earlier today, then looked at product reviews on desktop — they're in a late-consideration stage"
- "This user has searched for related queries across three devices over two weeks — they're a high-intent, long-consideration buyer"
- "This user converts primarily on desktop after initial mobile touchpoints — mobile bids should favor engagement over immediate conversion"
These cross-device signals feed into the AI's real-time bid adjustments. You don't configure this; it's inherent to how AI Max's auction prediction works.
The June 2026 Deletion's Impact on Cross-Device Data
The June 2026 data deletion (https://yositeup.com/blog/google-ads-reporting-data-deleted-june-2026) created gaps in the AI's cross-device attribution chains. Cross-device attribution requires linking events across touchpoints — when reporting data is deleted, conversion paths that spanned the deletion period lose some touchpoint records.
This means:
- Reporting impact: Cross-device conversion reports for campaigns active during the deletion period show fewer conversions than actually occurred (the missing ones had attribution paths that crossed the deleted data period)
- AI learning impact: The deleted period represents a gap in the AI's historical training data for cross-device patterns. The AI should have rebuilt its device-signal understanding over the weeks since deletion, but you may see residual effects in bidding patterns for longer-consideration products where the AI accumulated less device-path data during the deletion window
Actionable response: If you have a high-ticket or long-consideration product (where cross-device journeys are common), set a longer conversion window in your AI Max campaign settings. A 90-day conversion window captures more device-path completions and gives the AI more signal to work from — particularly important after a data disruption.
Cross-Device Attribution Settings in AI Max vs Classic Campaigns
In classic keyword campaigns, cross-device attribution required configuring "Cross-device conversions" in your Google Ads conversion settings. For AI Max, cross-device attribution is on by default and the AI uses it directly in bidding decisions.
You can review your cross-device conversion data in Google Ads: Reports > Predefined Reports > Extensions > Cross-device activity. This shows the attribution paths across devices — which devices initiated and which completed conversions.
For AI Max campaigns, this report helps you understand what the AI is optimizing toward. If 60% of your conversions have a mobile initiation and desktop completion path, the AI knows this and is adjusting mobile bids to capture that initiation traffic even though mobile "conversion rate" in last-click attribution looks low.
DSA Migration and Cross-Device History
When migrating DSA to AI Max for Search (https://yositeup.com/blog/google-ads-dsa-ai-max-migration-february-2027), DSA campaign's cross-device history doesn't directly transfer to the new AI Max campaign. The AI Max campaign starts building its own device-pattern understanding from its own conversion data.
For the first 4-6 weeks after DSA migration, the AI Max campaign is in its cross-device learning phase — it's seeing which device patterns in your account's audience actually convert. This is a reason not to make major bid strategy changes in the early weeks after migration.
AI Max for Shopping and Connected TV Attribution
AI Max for Shopping (https://yositeup.com/blog/google-ai-max-shopping-replacing-performance-max-2026) extends cross-device attribution to include Connected TV (CTV) ad impressions (when the AI serves Shopping-adjacent video ads on smart TV inventory). If a user sees your brand on TV, then searches and converts on desktop, AI Max for Shopping can attribute the TV view as part of the conversion path.
This is part of Performance Max's legacy that carries into AI Max for Shopping. The implication for reporting: if you added CTV placement coverage in AI Max for Shopping, your last-click Google Ads data will undercount the actual assisted conversion value from CTV. Check the attribution model comparison in Google Ads to see data-driven vs. last-click attribution differences — a gap indicates assisted touchpoints (CTV, mobile) are contributing.
July 2026 ToS and Cross-Device Data Usage
The July 2026 ToS update (https://yositeup.com/blog/google-ads-tos-july-2026-ai-automation-what-changed) references how AI can use audience signals. Cross-device attribution is one of the areas where the AI's data usage is most extensive — it's drawing on the Google identity graph across devices.
For advertisers in regulated categories: the ToS specifies how audience signals can be used, which includes cross-device data. If your campaign is in financial services, healthcare, or another sensitive category, review the updated ToS provisions specific to your category for any constraints on cross-device signal usage in AI Max.
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