remove duplicate purchase events in Meta Pixel

[Jinyoung]

A duplicate purchase event issue has occurred.

The screen shows an error like the one below. How can I fix this issue?

It seems that I need to add event_id to the payload. Please help!

[Kudosi-Tracy]

Hi @Jinyoung, 

You're right - adding an event_id to the payload should help prevent duplicate purchase events. The event_id acts as a unique identifier, allowing platforms like Facebook Pixel or Google Analytics to recognize and deduplicate events.

Here’s how to fix it:

1. Locate the purchase event code in your Shopify theme or tracking setup.

2. Modify the payload to include an event_id. If using Facebook Pixel, the event should look like this:

   fbq('track', 'Purchase', { value: 100.00, currency: 'USD', event_id: '{{ order.order_number }}' // Use a unique identifier });

3. If you're using Google Tag Manager, ensure that the event_id is passed dynamically in the data layer.

4. Test the fix using Facebook’s Event Manager or your analytics tool’s debugger.

Let me know if you need more details!

Best,
Tracy from Kudosi Reviews

[J_mah]

hi jiny,

Thanks for your query.

If you configure meta pixel and conversion API (CAPI), via google tag manager send event ID as event parameter with event tags both for meta pixel tag and server tag.

Feel free to ask if you have any questions.

Thanks

[Shanthi_Vutukur]

I read the other provided answers in this thread. I am assuming you have got your answer. 

And if you are using these Meta pixels for your Shopify store, then just as an alternative, you can also go with an app like AdNabu’s Facebook pixel app to avoid deduplication. It is a free app, allows you to create Meta (Facebook) pixels within minutes, and uses Conversions API to avoid deduplication. 

Thought, might help you : ) 

[CedarJovan]

The duplicate purchase event issue happens when Meta Pixel records the same purchase twice, messing up your tracking. You’re right—adding an event_id can help fix it.

Here’s how to solve it:
Check if the event is firing twice

Use the Meta Pixel Helper Chrome extension or go to Meta Events Manager > Diagnostics to see if two purchase events are logged for the same order.
If you see a duplicate warning, that confirms the issue.
Add an event_id to prevent duplicates
If you're using GTM or custom code, update your purchase event to include a unique event ID:

javascript
Copy
Edit
fbq('track', 'Purchase', {
value: 100.00,
currency: 'USD',
event_id: '{{ORDER_ID}}' // Make sure this is unique for each order
});
Replace {{ORDER_ID}} with a real order ID or timestamp.
This helps Meta recognize and ignore duplicate events.
Check for extra tracking scripts

If you've manually added a purchase event in GTM or in Shopify’s Additional Scripts section, it might be firing twice.
Go to Shopify Admin → Settings → Checkout → Additional Scripts, and remove any duplicate purchase tracking.
Clear cache & test again

After making changes, clear your browser cache and use Meta Pixel Helper or the Test Events tool in Meta Business Manager to check if the issue is fixed.
Let me know what tracking setup you're using (Shopify’s built-in pixel, GTM, or something else), and I can guide you better!