Why most agencies are losing 30–40% of their conversion data — and how to fix it.
Pixel = fires in browser (blockable) · CAPI = fires on server (not blockable) · event_id = deduplicates both
Most agencies are optimizing campaigns with half the data.
When you only install the Meta Pixel on your site, events are sent through the user's browser. But browsers have ad blockers, cookie restrictions, iOS 14, Safari ITP. Depending on your audience, 30 to 40% of events disappear before reaching Meta.
The campaign algorithm learns from what it receives. Less data means worse optimization and higher CPL — even without changing copy, creatives, or budget.
The Conversions API (CAPI) is a server-side integration launched by Meta in 2021. Instead of relying on the browser to send events, you send them directly from the server to Meta via an HTTP call. No ad blocker can intercept that.
The critical point is deduplication. Since the Pixel and CAPI both fire for the same event, Meta needs to know they're the same — otherwise it counts twice and distorts the data. The solution is a unique event_id generated on the frontend and sent to both channels.
→ If the Pixel is blocked, only CAPI counts. If both arrive, Meta uses event_id to avoid duplication.
CAPI requires some mandatory fields and accepts optional data that improves match quality — the more user data you send, the better Meta can attribute the event to a real person.
→ Optional fields increase the Event Match Quality Score — Meta's metric for measuring the quality of the received signal.
On the POSTEP site itself we use N8N as a relay between the frontend and the Graph API. The frontend sends a POST to an N8N webhook, which builds the correct payload and calls the Meta API server-side.
No external SDK dependency. N8N is already in the infra — the relay adds no cost, it just connects what already exists.
Depends on your audience. If most of your traffic is mobile iOS or uses ad blockers, the difference is immediate. If it's Android traffic without blockers, the gain is smaller — but the signal still improves.
high — 30–40% of events recovered
high — 100% of blocked events recovered
medium — improves Event Match Quality
high — algorithm receives more complete signal
If you're running conversion campaigns on Meta and don't have CAPI configured, you're optimizing with incomplete data. Implementation takes less than a day. The impact is immediate.