If your Google Ads conversion numbers have started looking odd against what GA4 is showing, you are not imagining it. Several agencies have flagged conversion volume drops, weaker enhanced conversion match rates, and audience lists suddenly marked as “too small to use”, with some pointing to changes in how GA4 and Google Ads exchange data through 2026. Google has not confirmed a single named update behind any of this, and we are not going to state unverified details as fact. What we do know is that Smart Bidding runs entirely on the conversion data it is fed, so a proper tracking health check is worth doing regardless of whether any of this applies to your account.
Why it’s worth checking now
Smart Bidding strategies do not know the difference between a genuine drop in conversions and a tracking fault. They only see the numbers coming in and adjust bids accordingly. If conversion volume quietly drops, or enhanced conversions stop matching as reliably as they used to, the algorithm will happily optimise towards a smaller or noisier signal without flagging that anything has changed. By the time it shows up in performance, several weeks of spend may already have been steered on bad data.
Even setting aside any platform-level changes, GA4-to-Ads integrations drift over time on their own – a new key event gets added and never imported, a tag gets updated by a developer without anyone checking downstream, an account handover leaves a gap in ownership. That is reason enough to run this kind of check periodically, not just when something already looks wrong.
Check that your GA4 key events match your Google Ads conversion actions
Start in GA4 under Admin > Events, and confirm which events are currently marked as key events. Then go to Google Ads under Goals > Conversions and check the imported GA4 actions against that list. Look specifically for conversion actions with a status other than active – “no recent conversions” or “needs attention” both mean Google Ads is not receiving what you think it is.
It is also worth double-checking which conversion actions are set as primary versus secondary, particularly if you use Target CPA or Target ROAS bidding. If a key event that matters for bidding has slipped to secondary, or a low-value event has ended up primary, that will skew optimisation even if the data itself is technically flowing correctly.
Check your enhanced conversions match rate
Enhanced conversions work by hashing customer data (email, phone, address) and matching it against signed-in Google accounts. The match rate for this sits under each conversion action’s diagnostics tab in Google Ads. If you notice this has dropped noticeably from where it normally sits, it is worth investigating before assuming it will recover on its own.
Common causes worth ruling out first: a form field mapping that has broken after a website update, a change to how consent is captured on the form itself, or the enhanced conversions tag simply not firing on a page it used to. A gradual, unexplained decline is worth flagging even if you cannot immediately identify the cause.
Check audience list sizes for “too small to use” warnings
Audiences below Google’s minimum size threshold cannot be used for targeting or bidding, and they will be marked accordingly in Audience manager within Google Ads, as well as under Admin > Audiences in GA4. If a remarketing or similar list that was previously healthy has started showing this warning, it is worth checking whether the underlying data feeding it – typically the GA4-Ads link and the audience trigger conditions – is still populating as expected.
This is easy to miss because a shrinking audience does not throw an obvious error in the campaign itself – it simply stops being eligible to serve, and spend or reach quietly reallocates elsewhere.
Check that GA4 and Google Ads conversion counts roughly reconcile
GA4 and Google Ads will rarely show identical numbers for the same event, since they use different attribution models and counting logic. A moderate variance is normal and not something to chase. What is worth investigating is a sudden or large divergence – pull the last 30 days for the same event in both platforms and look for an order-of-magnitude gap rather than a small percentage difference.
If the two have historically tracked fairly closely and have recently pulled apart, that is a stronger signal than the absolute numbers themselves, and worth prioritising over a one-off check of either platform in isolation.
Check Consent Mode is configured correctly
For UK and EEA traffic, Consent Mode directly affects how much conversion data you receive and how much is modelled rather than observed. If the consent banner is not passing consent state signals correctly, or if a recent cookie banner update has changed default consent settings without anyone checking the tagging implementation, conversion counts can understate reality independent of anything happening on Google’s side.
Worth checking specifically: that Consent Mode v2 is implemented (not the older version), that consent state fires before the tags that depend on it, and that the banner itself has not changed its default state as part of an unrelated CMP update.
None of the above requires a confirmed platform update to be worth doing. Tracking setups degrade quietly, and Smart Bidding will not tell you when it is working from a weaker signal than it used to.
If you’d rather have someone check this for you, tracking health is one of the first things we look at in a free audit. We check your conversion actions, enhanced conversions and Consent Mode setup against what GA4 is reporting, whether or not you work with us. No commitment, response within one business day.