Non-biddable conversions may be feeding Smart Bidding without your knowledge

Google quietly updated its Conversion Goals documentation to confirm non-biddable conversions can enhance Smart Bidding predictions.

Most accounts have not processed what that means.

Non-biddable conversions are the ones you mark as observation only. Phone calls you track but do not bid toward. Scroll depth events. Newsletter signups. You add them to understand behaviour, not to train the algorithm.

Except Google is now confirming they may influence how Smart Bidding weights its predictions. Not directly. Not visibly. As input to a model you cannot audit.

Why this changes the cost of bad signal

The practical implication is real. If you have sloppy non-biddable events, events that fire incorrectly, that capture noise rather than intent, those signals may be feeding the bidder in ways you cannot see and cannot switch off.

This is not a theory about how machine learning works. It is how machine learning works. More signal, better model. The question is whether the signal is clean.

Smart Bidding has always been a black box. This is another layer of opacity, and it is operating whether you read the documentation or not.

Where the noise comes from

In audit after audit, the same patterns turn up in the non-biddable column:

• Scroll-depth events that fire on every page load because of a bug in the GTM trigger
• Newsletter signup conversions counting form views, not actual submissions
• Phone-call conversions that include receptionist transfers and wrong-number calls
• "Engaged session" events firing on any session longer than 10 seconds, including bounce
• Form-abandonment events counted as engagement signals when they are actually failures
• Cross-domain conversions firing twice because of GTM duplicate trigger conditions
• Video-play events triggering on autoplay even when the user did not initiate

Each one looks defensible in isolation. Stacked together as the model's training signal, they push the bidder toward "engagement" patterns that do not correlate with revenue.

The audit

For every non-biddable conversion in your account:

• Confirm what it actually fires on (page load? click? form submit? scroll?)
• Confirm the trigger condition is correct (test with a clean session)
• Confirm the volume looks plausible against the underlying user behaviour
• Confirm whether the conversion correlates with downstream revenue at all
• If the signal is noisy or non-revenue-correlated, delete it or rebuild it

The mistake is assuming non-biddable means non-influential. It does not. Google has now confirmed it never did.

What to actually do

• Audit every non-biddable conversion this month. The exercise takes two hours on most accounts.
• Delete events that capture noise. Newsletter signup tracking with a 90 percent bot rate, scroll depth that fires before the page renders, time-on-site events triggered by autoplay video. Delete them, do not reclassify.
• Rebuild the events that should exist but have implementation issues. GTM trigger conditions, deduplication windows, cross-domain handling. The cleanup is one engineering ticket per problem.
• Treat every event in your account as potentially load-bearing, because at some point it probably is.
• Add the non-biddable audit to your quarterly tracking review. Drift is inevitable. Catching it before it changes bidder behaviour is the win.

Audit your non-biddable conversions. Delete the ones capturing noise.

If you want a free audit of every conversion event in your account and whether it is helping or hurting the bidder, book a free audit. We will catalogue every signal before recommending any campaign-level change.