Google Ads Conversion Tracking
Google Ads Conversion Tracking is the JavaScript tag that reports conversions, leads and ecommerce events back to Google Ads. It writes the _gcl_au and _gcl_aw advertising cookies, transmits the click identifier (gclid) and is required for bid optimisation and remarketing audiences. As an advertising tool, it requires prior consent under GDPR and ePrivacy and must be deployed with Google Consent Mode v2 in the EU.
What does Google Ads Conversion Tracking do?
What is Google Ads Conversion Tracking?
Google Ads Conversion Tracking is the JavaScript pixel that advertisers add to their site to report conversions, leads, sign ups and ecommerce purchases back to Google Ads. The tag is fired on success pages or specific events and connects each conversion to the corresponding ad click using the gclid parameter. It is the foundation of bidding strategies such as Maximise Conversions, Target CPA and Target ROAS, and feeds remarketing audiences.
Cookies and identifiers
The conversion tag writes _gcl_au and _gcl_aw on the advertiser domain to attribute the visit to a previous Google Ads click and reads cookies on doubleclick.net for cross device measurement. Enhanced conversions additionally send hashed email addresses or phone numbers, which are personal data even after hashing under European supervisory authority guidance.
GDPR and ePrivacy implications
The conversion pixel is an advertising technology, not strictly necessary for the website. Article 5(3) of the ePrivacy Directive therefore requires prior consent before the tag fires. The CNIL, AEPD, BfDI and Garante have all emphasised that conversion measurement performed through Google Ads constitutes processing for advertising purposes and must be opt in.
Google Consent Mode v2
Since March 2024, advertisers serving EEA traffic must implement Consent Mode v2 to keep using audiences and modelled conversions. Consent Mode v2 introduces ad_user_data and ad_personalization signals that must reflect the visitor's real choices in the cookie banner. Without consent, the tag should send no cookies and the conversion ping must be in the basic mode with no identifiers.
Data transfers to the United States
Conversion data, IP addresses and identifiers are transmitted to Google LLC infrastructure in the United States. Google self certifies under the EU U.S. Data Privacy Framework, but you should still document the transfer in your records of processing and inform visitors in the privacy policy.
Implementing conversion tracking compliantly
Block the conversion tag in your tag manager until the visitor accepts the marketing category. Configure Consent Mode v2 with the four signals (ad_storage, analytics_storage, ad_user_data, ad_personalization) wired to your CMP. Use server side tagging when possible to limit the data sent client side, and document every conversion action in your records of processing.
Google Ads Conversion Tracking and the GDPR
Google Ads Conversion Tracking is classified as “Marketing”. On a site that targets European visitors, it must only load after the visitor consents, and it must be listed in your cookie policy.
- Legal basis
- Prior consent under Article 6(1)(a) GDPR and Article 5(3) of the ePrivacy Directive, since the conversion tag writes and reads non essential advertising cookies (gcl, gcl_aw) and shares behavioural data with Google.
- Risk level
- high
- Applicable regulations
- GDPR, ePrivacy Directive, EU U.S. Data Privacy Framework, Google Consent Mode v2 requirements
Impact assessment (DPIA)
A DPIA should be considered when conversion tracking is combined with enhanced conversions (hashed email, phone), customer match audiences or remarketing, due to identification of users, transfers to the United States and large scale ad profiling.
Sample text for your banner
We use Google Ads Conversion Tracking to measure ad campaign performance. With your consent, Google may store advertising cookies on your device, link your visit to a previous ad click and transfer data to Google LLC in the United States. You can refuse or withdraw your consent at any time from the cookie settings.
What Google Ads Conversion Tracking sets and contacts
- Tracking method
- JavaScript conversion tag (gtag.js or googleads.g.doubleclick.net pixel) that fires after a conversion event and sends the click identifier (gclid), conversion label and event metadata to Google Ads servers.
- Server location
- United States (Google global infrastructure)
- Data transferred outside the EU
- Conversion data, IP addresses and identifiers (gclid, _gcl_au) are transferred to Google LLC servers in the United States under the EU U.S. Data Privacy Framework.
Cookies set (4)
| Name | Type | Duration | Purpose |
|---|---|---|---|
| _gcl_au | first_party | 90 days | Set on the advertiser domain by Google Tag Manager to attribute the visit to a previous Google Ads click for conversion measurement. |
| _gcl_aw | first_party | 90 days | Stores the gclid identifier on the advertiser domain to link a conversion to the originating Google Ads click. |
| IDE | third_party | 13 months | Set on doubleclick.net for conversion attribution and cross device measurement in Google Ads. |
| test_cookie | third_party | 15 minutes | Set on doubleclick.net to verify that the browser supports cookies before serving the conversion ping. |
Third-party domains contacted (5)
googleads.g.doubleclick.netwww.googletagmanager.comwww.google.comdoubleclick.netgoogleadservices.com
Frequently asked questions about Google Ads Conversion Tracking
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Which cookies does Google Ads Conversion Tracking set?
The conversion tag writes _gcl_au and _gcl_aw on the advertiser domain to attribute the visit to a previous Google Ads click, plus the third party cookies IDE and test_cookie on doubleclick.net for cross device measurement.
Does Google Ads Conversion Tracking require consent?
Yes. The pixel is an advertising tool that writes non essential cookies and shares behavioural data with Google, so prior, specific and informed consent is required under Article 5(3) of the ePrivacy Directive and Article 6(1)(a) GDPR.
What is the legal basis for using it?
Consent is the only suitable legal basis. Legitimate interests cannot be relied on because the processing involves cross site profiling for advertising purposes and transfers to the United States.
Are conversion data transferred to the United States?
Yes. The conversion ping, IP address, gclid and any enhanced conversion identifier are sent to Google LLC in the United States under the EU U.S. Data Privacy Framework. The transfer must be disclosed in your privacy policy.
Do I need a DPIA for conversion tracking?
A DPIA is recommended when conversion tracking is combined with enhanced conversions, customer match audiences or extensive remarketing, due to user identification, US transfers and large scale advertising profiling.
How do I deploy it compliantly?
Block the tag through your CMP until consent is granted, configure Google Consent Mode v2 with all four signals, prefer server side tagging via Google Tag Manager Server, and document the legal basis and retention in your records of processing.
Are there alternatives to Google Ads Conversion Tracking?
Privacy first alternatives include first party server side conversion APIs (Google Ads API offline conversions, Plausible Goals, Matomo Goals) which limit the data shared with Google and avoid client side cookies altogether.
How do I update my cookie policy?
Add a section that names Google Ads Conversion Tracking, lists the cookies (_gcl_au, _gcl_aw, IDE, test_cookie) with purpose and duration, mentions the transfer to Google LLC in the United States and links to Google's privacy policy.
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