Google Ads Deprecates Legacy Attribution Models
On September 24, 2026, industry experts highlighted a major attribution reset hitting advertisers as Google Ads officially deprecated first-click, linear, time-decay, and position-based attribution models. This matters because your Q4 data will not match last year, making year-over-year performance comparisons incredibly difficult. All conversion actions using those deprecated models were automatically upgraded to data-driven attribution (DDA), forcing a massive shift in how your account measures success.
What changed
- Google Ads officially deprecated first-click, linear, time-decay, and position-based attribution models.
- All conversion actions using those models were automatically upgraded to data-driven attribution.
- GA4 added a new channel for traffic coming from AI chat assistants.
- Shopify enabled storefronts that process orders entirely within third-party environments.
Why it matters for your numbers
These simultaneous shifts mean that your historical data is no longer directly comparable. If you have been using linear or time-decay models to understand how your top-of-funnel campaigns assist conversions, those insights are now gone. Google's data-driven attribution uses machine learning to distribute credit, which often favors their own high-intent search and shopping campaigns.
Furthermore, the introduction of a new GA4 channel for AI assistants and Shopify's storefronts that process orders within third-party environments will heavily skew your Q4 comparisons. You are dealing with an entirely different measurement landscape than you were last year. If you try to compare this year's Q4 ROAS to last year's using native platform dashboards, you will be looking at completely different attribution rules, leading to incorrect conclusions about your campaign health.
When an ad platform forces a change like this, the immediate reaction for many media buyers is to panic. You might see your reported ROAS drop or shift dramatically overnight, leading to the temptation to turn off campaigns that look like they are underperforming. This is a mistake. The actual performance of your ads has not changed; only the way Google reports them has. To survive Q4, you need a stable, independent source of truth that does not rely on the shifting sands of Google's native attribution models.
What I would do
- When platform models break, never panic and pause your campaigns.
- Focus on securing accurate, independent reporting so you can see actual performance before making decisions.
- Switch to a professional, independent third-party tracking and attribution solution to maintain a consistent baseline of performance data.
- Rebuild your reporting dashboards to account for data-driven attribution defaults and the rise of AI-referred, storefront-less orders.
- Document the exact date of this attribution reset in your internal notes so your team knows why year-over-year metrics look different.
TrueROAS bypasses platform-level model changes by tracking your actual orders server-side, giving you a consistent source of truth that does not change when Google resets its rules.
Source: Braivex
If your numbers look off after this week, grab 20 minutes with me and we will look at your attribution together: Book a call with Rasmus.
