Recovering abandoned carts is one of the highest ROI email automations in eCommerce. When combined with OpenCart’s event data and GA4’s behavioral insights, you can build a powerful system that auto-triggers emails only to engaged, identifiable users who abandon without converting.

🧰 Prerequisites

Platform/Tool	Purpose
OpenCart v3.x / 4.x	Storefront + editable theme files
Google Tag Manager	Pushing events into GA4
GA4 + BigQuery	Event collection and audience queries
Email Platform (e.g. Klaviyo)	Email automation via API or CSV import

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🔄 Flow Overview

OpenCart ➜ dataLayer ➜ GTM ➜ GA4 ➜ BigQuery ➜ Query abandoned carts ➜ CRM ➜ Email

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📦 Step 1: Push add_to_cart Event from OpenCart

Update product.twig or JS add-to-cart handler to send data to GTM:

<script>
document.querySelector('.btn-add-to-cart').addEventListener('click', function () {
  window.dataLayer = window.dataLayer || [];
  dataLayer.push({
    event: "add_to_cart",
    product_id: "{{ product.product_id }}",
    product_name: "{{ product.name }}",
    product_price: "{{ product.price }}",
    email: "{{ email if customer_logged_in else '' }}"
  });
});
</script>

✅ If email is not available on frontend, collect it at checkout entry or via login field.

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💳 Step 2: Push purchase Event on Success Page

Edit success.twig (after order placement):

<script>
dataLayer = dataLayer || [];
dataLayer.push({
  event: 'purchase',
  transaction_id: '{{ order_id }}',
  email: '{{ email if email else customer.email }}',
  value: {{ total }}
});
</script>

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🛠️ Step 3: Configure GA4 Tags in GTM

Create two GA4 Event Tags:

A. GA4 – add_to_cart

• Event Name: add_to_cart
• Parameters:
  • product_id: {{DLV - product_id}}
  • product_name: {{DLV - product_name}}
  • product_price: {{DLV - product_price}}
  • email: {{DLV - email}} (if available)
• Trigger: Custom Event = add_to_cart

B. GA4 – purchase

• Event Name: purchase
• Parameters:
  • transaction_id: {{DLV - transaction_id}}
  • value: {{DLV - value}}
  • email: {{DLV - email}}

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🧠 Step 4: Store GA4 Events in BigQuery

1. Go to GA4 > Admin > BigQuery Linking
2. Enable daily or streaming export
3. GA4 data will populate in:
   project.dataset.events_*

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🔍 Step 5: Write SQL Query to Find Abandoned Carts

Abandoned cart = add_to_cart exists but purchase doesn’t.

WITH cart_events AS (
  SELECT
    user_pseudo_id,
    event_date,
    MAX(IF(event_name = 'add_to_cart', 1, 0)) AS added_to_cart,
    MAX(IF(event_name = 'purchase', 1, 0)) AS purchased,
    MAX(IF(event_name = 'add_to_cart', value.string_value) FILTER(WHERE key = 'email')) AS email
  FROM
    `project.dataset.events_*`
  WHERE
    _TABLE_SUFFIX BETWEEN FORMAT_DATE('%Y%m%d', DATE_SUB(CURRENT_DATE(), INTERVAL 2 DAY))
                      AND FORMAT_DATE('%Y%m%d', CURRENT_DATE())
  GROUP BY user_pseudo_id, event_date
)
SELECT *
FROM cart_events
WHERE added_to_cart = 1 AND purchased = 0 AND email IS NOT NULL

✅ Export the result to CSV or use directly in Zapier/Cloud Function for automation.

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📬 Step 6: Trigger Emails from CRM (Klaviyo, Mailchimp, etc.)

Option A: Klaviyo via API

1. Send data via POST to Klaviyo /profiles/ or /events/ endpoint
2. Use email as identifier
3. Trigger a flow in Klaviyo for new abandoned cart entry

{
  "data": {
    "type": "event",
    "attributes": {
      "profile": {
        "email": "user@example.com"
      },
      "metric": {
        "name": "Abandoned Cart"
      },
      "properties": {
        "product_name": "OpenCart T-shirt",
        "cart_value": "29.99"
      },
      "timestamp": "2025-06-04T12:00:00Z"
    }
  }
}

Option B: CSV Import (Manual / Zapier)

• Download your BigQuery output
• Import into Mailchimp/Klaviyo segment
• Trigger automation from the list

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✅ Optional: Add Deduplication Logic

To prevent re-triggering for same cart:

• Store sent user_pseudo_id + event_date in Firestore or Sheets
• On next query, exclude previously used users

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🧪 Step 7: QA the Journey

Tool	Use
GTM Preview	Ensure event firing
GA4 DebugView	Validate add_to_cart and purchase
BigQuery	Check email field population
Klaviyo Logs	Confirm abandoned cart event appears

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📈 Bonus: Add Engagement Thresholds

To avoid low-quality email triggers:

• Add filter: session_engaged = TRUE in GA4 events
• Or engagement_time_msec > 10000

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