🔴 Phase 1 — Core · The single most important event. Drives revenue, ROAS, and Google Ads conversions.

purchase ⭐

When to push

On the order confirmation page (/checkout/success, /order/thank-you, etc.), after the order is committed to the database.

⚠️ Exactly once per order. See idempotency.

Complete example

window.dataLayer.push({ ecommerce: null });
window.dataLayer.push({
  event: 'purchase',
  ecommerce: {
    transaction_id: 'ORD-2026-00123',     // REQUIRED, unique
    currency: 'EUR',
    value: 109.00,                         // merchandise (excl. shipping/tax)
    tax: 18.17,
    shipping: 4.95,
    coupon: 'SPRING10',
    affiliation: 'Biosphere Online Store',
    items: [
      {
        item_id: 'BIO-CRM-001',
        item_name: 'Hydrating Day Cream',
        item_brand: 'Biosphere',
        item_category: 'Skincare',
        item_category2: 'Face',
        item_variant: '50 ml',
        price: 42.00,
        quantity: 2,
        discount: 0
      },
      {
        item_id: 'BIO-SER-002',
        item_name: 'Radiance Serum',
        item_brand: 'Biosphere',
        item_category: 'Skincare',
        item_category2: 'Face',
        price: 25.00,
        quantity: 1,
        discount: 10.00
      }
    ]
  },
  user_data: {
    email: 'jane.doe@example.com',
    phone: '+33612345678',
    first_name: 'Jane',
    last_name: 'Doe',
    address: {
      street: '12 Lilac Street',
      city: 'Paris',
      region: 'IDF',
      postal_code: '75011',
      country: 'FR'
    },
    external_id: 'user_12345'
  }
});

Parameters

Event level

Parameter	Type	Required
transaction_id	string	REQUIRED — unique per order
currency	string	REQUIRED
value	number	REQUIRED — merchandise, excl. shipping/tax
items	array	REQUIRED
tax	number	recommended
shipping	number	recommended
coupon	string	optional
affiliation	string	optional

Item level

All standard fields (items). Critical to include:

• item_id (must match Meta Catalog)
• price (after item-level discount)
• quantity
• discount (if item-level discount applies)

user_data REQUIRED

Send everything you have about the customer. The more complete, the better Meta matches (target EMQ ≥ 8) and the more accurate the Google Ads attribution (Enhanced Conversions). See user_data.

Platforms

Platform	Native event	Notes
GA4	purchase	Revenue, ROAS, transactions
Meta	Purchase	CAPI + Pixel, deduped via event_id, contents for DPA
Google Ads	Conversion + Enhanced Conversions	Hashed user_data uploaded

The transaction_id is sacred

Without a unique transaction_id:

• GA4 dedupes badly → revenue inflated on every refresh.
• Meta CAPI counts twice → ROAS/CPM corrupted.
• Google Ads conversion may be rejected.

Rules:

• Unique per order.
• Stable (never regenerated).
• Ideally = customer-facing order number.
• String, max 100 chars.

Amount consistency

value (merchandise) = Σ (item.price × item.quantity) - global coupons
total paid          = value + tax + shipping

GA4 reports value as revenue. The total paid is reconciled by summing.

Fatal pitfalls

• ❌ No transaction_id or non-unique.
• ❌ Push before DB commit → ghost revenue if payment fails async.
• ❌ Re-push on refresh → double counting.
• ❌ value includes shipping/tax → inflated ROAS.
• ❌ Cents instead of units (10900 instead of 109.00).
• ❌ item_id ≠ Meta Catalog → DPA audiences broken.
• ❌ Pushing without user_data → Meta EMQ ~ 3/10, massive signal loss.