What is the difference between conversion and remarketing in gtag.js?

A conversion event (send_to: AW-XXX/LABEL) reports a specific conversion action to Google Ads and is used for bid optimization. Remarketing is automatically activated with gtag('config', 'AW-XXX') and collects audience data on all page visits. A label is required for conversion but not for remarketing.

What is the difference between a purchase event and a conversion event?

conversion is a Google Ads-specific event name that directly reports a conversion. purchase is a GA4 ecommerce event, but when send_to specifies AW-XXX/LABEL, it is also sent to Google Ads as a conversion. Cart data parameters (aw_merchant_id, etc.) can only be sent with the purchase event.

Why doesn't the cart data signal reach 100%?

The most common reason is that items[].id does not exactly match the product IDs in the Merchant Center feed. Additionally, missing required parameters (aw_merchant_id, aw_feed_country, aw_feed_language), users blocked by consent mode, and the tag firing before the dataLayer is populated also reduce the signal.

What is the difference between id and item_id?

id is the parameter name used on the Google Ads side (remarketing, cart data). item_id is the GA4 ecommerce standard. Both are transmitted identically in network requests, and Google Ads accepts both. When sending to both destinations, defining both in the same object is recommended.

How do you send user_data for enhanced conversions?

It is defined at the global scope with gtag('set', 'user_data', { email: '...', phone_number: '...' }). This call must be made before the conversion event. Google automatically hashes the data with SHA-256. It can also be sent at the event level, but event-level user_data overrides the global set, it does not merge.

What happens if there is no label in the send_to parameter?

send_to: 'AW-XXX' (without a label) only sends remarketing data and does not count as a conversion. The label (AW-XXX/LABEL format) identifies a specific conversion action in Google Ads. Without a label, which conversion action to trigger cannot be determined.

Google Ads gtag.js: Conversion, Remarketing, and Cart Data Guide

A comprehensive look at conversion, remarketing, cart data, enhanced conversions, and consent mode structures in Google Ads gtag.js, the differences between them, and correct usage scenarios.

TL;DR

When sending data to Google Ads via gtag.js, conversion, remarketing, and cart data are distinct mechanisms. A conversion event requires a label in the send_to parameter; without a label, only remarketing data is transmitted. Cart data is sent with the purchase event using aw_merchant_id, aw_feed_country, and aw_feed_language parameters. Enhanced conversions improve conversion match accuracy through user_data (email, phone). A single purchase event with the right parameters can carry conversion, cart data, and remarketing data simultaneously.

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