This issue is quite common and usually stems from duplicate events being triggered—especially when both Facebook Pixel and Conversions API (CAPI) are firing simultaneously without proper deduplication.
Your Pixel and CAPI are both sending purchase events, but Facebook is not deduplicating them properly, resulting in inflated conversions.
How to Fix It:
Check Event Deduplication IDs:
In Meta Events Manager, look at the “Event ID” values.
For proper deduplication, both the browser (Pixel) and server (CAPI) events must share the same Event ID.
Use Shopify's Native Integration Only:
Since you’re already using the Facebook & Instagram app, avoid any other event tracking app or custom code.
Go to Settings → Customer events and ensure there’s only one active Pixel source.
Turn Off Manual CAPI (if added externally):
If you ever added CAPI manually via another app or API, it could still be sending events.
Double-check your apps and integrations in Shopify Admin → Apps and disable any third-party tracking tools that may still be active.
Test With Facebook Pixel Helper:
Contact Meta Support for Manual Deduplication Review:
Tip:
It’s okay for Pixel + CAPI to fire together if deduplication is correctly set up. The key is consistent event_name and event_id between both sources.