HELP PLEASE! Error: Purchase Event missing some Deduplication Parameters for FB Pixel

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Topic summary

A user encountered Facebook Pixel errors indicating missing deduplication parameters for Purchase, AddToCart, InitiateCheckout, and PageView events. Without deduplication keys, events are being double-counted when sent from both the Facebook Pixel and Conversions API, potentially affecting measurement and ad campaign optimization.

Recommended Solutions:

  • Verify Shopify’s Facebook & Instagram integration is properly configured, as it typically handles deduplication automatically
  • Enable Advanced Matching in Facebook Events Manager settings
  • Use Test Events to confirm both Pixel and Conversions API send matching event_id parameters
  • Add event_id parameter manually to event code if using custom implementations: fbq('track', 'Purchase', {value: 12, currency: 'USD'}, {eventID: 'UNIQUE_EVENT_ID'})

Alternative Approach:
Several respondents suggested using Google Tag Manager (GTM) to configure Meta Pixel and Conversions API, requiring datalayer setup and variable configuration. For non-technical users, hiring an expert or using specialized Shopify apps (like AdNabu’s Facebook Pixel app) was recommended to automate deduplication handling without coding.

Summarized with AI on October 30. AI used: claude-sonnet-4-5-20250929.
1

Hello! I have received this error today on Facebook and to be honest, none of the solutions make any sense to me! Is there a way to explain what I need to do and how? I am SO confused!

Issue: Purchase Event Missing Deduplication Parameter
Issue: AddToCart Event Missing Deduplication Parameter

Issue: InitiateCheckout Event Missing Deduplication Parameter

Issue: PageView Event Missing Deduplication Parameter

You haven’t sent a deduplication key for this event. Without a deduplication key, your Purchase events will be double counted because they can’t be deduplicated.

This may cause issues with the measurement of your events as well as the attribution and delivery optimization of any ad campaigns that are optimizing for this event.

Is someone able to tell me exactly what to do as all the sites I’m looking on are really confusing, clearly aimed at those who know what they’re doing! Thank you!

2

Hi LozLSP,

Thanks for your query.

Is your event deduplication fixed?

If not configure meta pixel and conversion API via google Tag Manager GTM. This could be error from facebook and Instagram app.

Kind Regards

3

Thank you! The issue I have is I’m not technical and am not sure how to do this!

4

There are some specific steps to be followed to achieve this goal:

  1. Datalayer setup on custom pixel

  2. Datalayer variable setup on GTM (value, currency, transaction ID, name , email)

  3. Create the conversion Action manually and set up the Google tag with the conversion ID and conversion Label

  4. Creation of a tag for the purchase event and assigning the variables as event parameters and triggers to fire the event and send it to the ads manager.

IF you are not technically sound it would be better to hire someone expert.

Feel free to ask if you have any questions regarding GTM.

Kind Regards

5

Hi @LozLSP

No worries! This error happens when Facebook receives the same event twice, once from the Facebook Pixel and once from the Conversions API but without a deduplication key to merge them. Here’s how to fix it:

  1. Check Shopify’s Facebook Integration

    • Go to Shopify Admin > Facebook & Instagram
    • Ensure your Facebook Pixel and Conversions API are both enabled. Shopify usually handles deduplication automatically.

  2. Verify Advanced Matching Settings

    • In your Facebook Events Manager, go to Data Sources > Your Pixel > Settings
    • Ensure Advanced Matching is enabled.

  3. Test Events in Facebook

    • Open Events Manager > Test Events
    • Visit your site in another tab, make a test purchase, and see if Shopify sends both Pixel and Conversions API events with matching event_id.

  4. Manually Set Deduplication (if needed)

    • If using custom code or apps for events, ensure the event_id is consistent between Pixel and API.
    • If unsure, try removing third-party apps that modify Facebook tracking and rely on Shopify’s default integration.

If the issue persists, reset the Facebook channel in Shopify and reconfigure it. Hope this helps :slightly_smiling_face:

6

As others have mentioned, these errors are occurring because Facebook is receiving duplicate events from your pixel and conversions API.

While that’s normal, what’s causing this problem is that there is no deduplication key to identify and merge these events.

To fix this issue, you should add the event_id parameter to both your pixel and conversions API events.

Here’s how you can modify your event code to add the event_Id parameter:

fbq(‘track’, ‘Purchase’, {value: 12, currency: ‘USD’}, {eventID: ‘UNIQUE_EVENT_ID’});

But instead of doing all this manually, I suggest you use a specialized Facebook pixel app that takes care of deduplication.

AdNabu’s Facebook Pixel app can be helpful. It’s a free app that handles deduplication with the help of Conversions API. It also allows you to create and implement pixels easily, without any coding.

Hope this helps!