Your store shows 300 orders this month. Meta Ads Manager reports 180 purchases from ads. The gap may not mean the ads are failing. More likely, measurement is missing sales.

The Meta pixel is code that runs in the browser and tells Meta when a visitor does something on your site. The trouble is that the browser is no longer as reliable a place as it was.

Why the pixel loses events

• App Tracking Transparency: with iOS 14.5 in April 2021, Apple made app tracking subject to user permission. Measuring people who decline became harder.
• Ad blockers: blockers and some browsers' built-in protections can stop pixel code from running at all.
• Short-lived cookies: some browsers cap cookie lifetimes, so someone who returns days later to buy may not be matched to their first click.
• Slow pages and early exits: if the thank-you page is closed before it loads, the purchase event may never fire.

What the Conversions API does

The Conversions API (CAPI) sends events to Meta from your server rather than the browser. The moment an order hits your database, the server tells Meta the purchase happened. No blocker can intervene, and it does not matter whether the page loaded.

CAPI does not replace the pixel; it completes it. The recommended setup runs both: the pixel sends the event from the browser, CAPI sends the same event from the server, and Meta merges them.

However clever the algorithm, an ad system learning from incomplete data keeps showing the right ad to the wrong people.

Why it matters so much

Meta's ad system learns who buys and finds similar people. Every under-reported sale is an example missing from its learning data. The damage runs both ways: your reported cost looks higher than it is, so you may switch off a campaign that works, and the algorithm optimises worse with less data.

Common setup mistakes

• Double counting: when the pixel and CAPI send the same event, both must carry the same event ID (event_id), or Meta counts the sale twice and results inflate.
• Thin customer data: match quality depends on what you send. Email and phone should be sent hashed, as Meta requires, and in line with privacy rules.
• Sending only purchases: add-to-cart, checkout started and form submissions also signal the algorithm.
• Skipping consent: clarify your obligations before sending data for users who declined cookies.
• Not checking: review event match quality and event counts in Events Manager regularly after setup.

How it gets set up

Shopify and some Turkish e-commerce platforms offer ready integrations you can switch on with a few settings. Custom sites need server-side development or server-side tag management. Either way, compare your store numbers with Meta's after setup; the gap should narrow.

Frequently asked questions

If I set up the Conversions API, can I remove the pixel?

Meta recommends running both. The pixel is good at capturing browser behaviour like page views and scrolling; CAPI makes sure critical events like purchases are not lost. Running them together with a shared event ID improves both coverage and match quality.

What is event match quality, and what should it be?

This score in Events Manager shows how well your events can be matched to Meta accounts. Sending complete, consented and hashed customer details such as email and phone raises it. Rather than chasing a fixed target, watch the score and event counts improve steadily after setup.

Is there something similar for Google Ads?

Yes. Enhanced Conversions and server-side tagging serve a similar purpose on Google: measuring conversions more completely and in a privacy-respecting way. If you advertise on several platforms, building measurement under one plan reduces upkeep.

The other half of measurement is seeing ad sources correctly in your own analytics, covered in our UTM guide. For how attribution windows mislead, see this piece. For setup and campaign management, see our performance marketing page.