Enhanced Conversions for Web is Google’s answer to the cookie deprecation problem. By sending hashed first-party customer data alongside standard conversion tags, you help Google match conversions to logged-in Google users even when browser cookies are blocked, deleted, or not set due to consent restrictions. Advertisers who implement Enhanced Conversions typically see a 5-15% increase in reported conversions and improved bidding accuracy. This guide covers the GTM implementation, the data requirements, and how to verify Enhanced Conversions are matching correctly.

How Enhanced Conversions Works

When a user completes a conversion on your site, Enhanced Conversions captures their email address (and optionally name, phone, and address) from your confirmation page, hashes it using SHA-256, and sends the hashed data to Google alongside the standard conversion event. Google then attempts to match the hashed email to a Google account. If the match succeeds, Google can attribute the conversion to the correct ad click even if the conversion cookie was not present. The match happens server-side at Google using a privacy-safe hashed comparison — Google never receives unhashed PII.

Setting Up Enhanced Conversions in GTM

First, enable Enhanced Conversions in your Google Ads account: Tools → Conversions → Settings → Enhanced Conversions → Turn on Enhanced Conversions for web. Select the GTM implementation method. Then in GTM, update your Google Ads Conversion Tracking tag to include user-provided data. You have two options: automatic collection (GTM scans page forms automatically) or manual data layer input (you push customer data to the dataLayer explicitly).

Manual data layer is more reliable. Push customer data to the dataLayer on your conversion confirmation page:

// Push enhanced conversion data on order confirmation page
dataLayer.push({
  event: 'purchase',
  enhanced_conversion_data: {
    email: '[email protected]', // Google will hash this
    phone_number: '+15551234567',
    first_name: 'John',
    last_name: 'Smith',
    street: '123 Main St',
    city: 'New York',
    region: 'NY',
    postal_code: '10001',
    country: 'US'
  },
  // Standard ecommerce data
  ecommerce: {
    transaction_id: 'order_12345',
    value: 99.99,
    currency: 'USD'
  }
});

In GTM, create Data Layer Variables for each field (enhanced_conversion_data.email, etc.). In your Google Ads Conversion tag, enable Enhanced Conversions and map each variable to the corresponding field. GTM will automatically hash the values before sending them to Google — you do not need to hash them yourself when using the GTM tag.

Email as the Minimum Viable Signal

Email address is the most important enhanced conversion field because it has the highest match rate with Google accounts. Phone number is second. Address fields (name, street, city) improve match rates when email alone does not match. For most implementations, email alone provides 80-90% of the match rate benefit. If your conversion page only has the email address available (for example, a lead form submission confirmation where you redirect immediately), email alone is sufficient to implement.

Verifying Enhanced Conversions in Google Ads

After deploying Enhanced Conversions, allow 2-4 weeks for data to accumulate before evaluating match rates. In Google Ads, go to Tools → Conversions, click your conversion action, and check the Enhanced Conversions diagnostics section. This section shows: the percentage of conversions with enhanced data, the match rate (how many enhanced conversion attempts successfully matched to a Google account), and any tag health issues.

A match rate above 40% is considered good. Rates below 20% indicate either data quality issues (email addresses that are not associated with Google accounts, formatting problems in the hashed data) or implementation errors (the enhanced_conversion_data is not being populated on the conversion confirmation page). Check your GTM Preview to verify the enhanced conversion variables are populated with actual email values when a test conversion fires, not undefined or null.

Enhanced Conversions and Consent Mode

Enhanced Conversions respects Consent Mode. If ad_user_data is set to denied for a user, the enhanced conversion data for that user will not be sent to Google, even if your GTM tag is configured to collect it. This is the correct behavior from a privacy compliance standpoint. The combination of Consent Mode and Enhanced Conversions is the recommended architecture for European advertisers: Consent Mode handles users who decline, and Enhanced Conversions maximizes match rates for users who consent. Together they provide the best possible signal quality within privacy constraints.