Your ad platform is optimising against conversion data that is 30–50% incomplete — and it isn't warning you.
This isn't a pessimistic take. Since Apple released iOS 14.5 in 2021, followed by increasingly strict Safari Intelligent Tracking Prevention and the steady growth of ad blockers among Thai internet users, client-side Pixel tracking can no longer capture every conversion.
The problem is that Meta and Google don't alert you when data goes missing. They keep optimising with whatever signal they receive — which means their algorithms are building audiences and setting bids based on half the picture.
The result: ad spend chasing the wrong people, ROAS lower than it should be, and decisions to scale or cut campaigns made on distorted data. This post explains what's happening, how to check if your account is affected, and how to fix it.
What Conversion Tracking Is and Why It Drives Everything
Conversion tracking tells your ad platform what users did after clicking your ad — filled a form, made a purchase, called your business, or downloaded a document.
This data doesn't just tell you how many sales came in. It's the primary signal Meta and Google's algorithms use to decide who to show your ads to, when, and at what bid price.
When tracking is complete, the algorithm learns which audience segments actually convert and finds more people like them. That's Smart Bidding in Google Ads and Advantage+ in Meta.
When tracking is broken, the algorithm is still optimising — just against incomplete data. Like navigating by a map with half the roads missing.
Why Your Pixel Is Losing Data: Three Simultaneous Forces
iOS App Tracking Transparency (ATT)
Since iOS 14.5, iPhone users must explicitly tap "Allow Tracking" for Meta's Pixel to follow behaviour across apps. Globally, around 60–70% of iOS users decline. In Thailand, that figure is likely higher among mid-to-high-income segments who skew iPhone-heavy. iOS 17 tightened this further with Private Click Measurement (which delays conversion reporting) and Safari's Intelligent Tracking Prevention (which deletes third-party cookies).
Ad Blockers and Browser Privacy
uBlock Origin, AdBlock Plus, and similar extensions — common among 18–35 year-olds in Thailand — block Meta Pixel and Google Tag requests directly. Firefox and Brave ship with tracking protection enabled by default. No install required.
ITP Cookie Expiry
Safari caps cookie lifetime at 7 days, sometimes 24 hours. If a customer researches your product over two weeks before buying, the conversion won't be attributed — the cookie expired before the sale.
Taken together, these three forces explain why most ad accounts under-report conversions by 30–50%. Businesses where customers skew iPhone-heavy can see gaps above that. See how we address this in our Meta Facebook Ads management service.
Three Ways to Check If Your Account Is Affected
1. Compare Platform Conversions to Actual Sales
Pull your Meta Ads Manager or Google Ads conversion report and compare it against real sales data from your CRM, POS, or order database for the same period. A gap of more than 20% is a clear signal of tracking loss.
2. Check Event Match Quality in Meta
In Meta Events Manager, look at the Event Match Quality Score for your Pixel. Anything below 6/10 means Meta is struggling to match events to user accounts — which degrades the quality of the audiences your algorithm builds.
3. Check Modelled Conversions in Google Ads
Go to Columns → Conversions → Modelled Conversions. A high modelled conversion count means Google is estimating your conversions because it's not receiving enough direct signal. In a healthy account, modelled conversions should be a small fraction of total.
The Fix: Server-Side Tracking and CAPI
The correct solution is moving your conversion signal from client-side (the user's browser) to server-side (your server) — where iOS ATT, ad blockers, and ITP have no reach.
Meta Conversions API (CAPI)
CAPI lets you send conversion events directly from your server to Meta's servers, bypassing the browser entirely. iOS users who tapped "Don't Allow" and users with ad blockers are still tracked.
Best practice: run CAPI alongside Pixel with proper deduplication parameters, so Meta knows when an event came from both channels rather than counting it twice.
Google Enhanced Conversions
Enhanced Conversions works by sending hashed user data — email address or phone number from a form submission — to Google for matching against signed-in Google accounts. Conversions are captured even when cookies are gone.
Server-Side Google Tag Manager (sGTM)
sGTM runs Google Tag Manager on your own server rather than the user's browser. All tracking events originate server-side, making them immune to client-side blocking. Most comprehensive solution, but requires technical setup and maintenance.
Running Google Ads? See our Google Ads campaign management service for how we handle this end-to-end. For the technical spec, Meta's Conversions API documentation is the authoritative reference.