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Data Privacy Unlocked: What Marketing Leaders Must Know About Meta & Google Retargeting

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In today’s digital marketing ecosystem, retargeting ads have become a critical lever for driving conversions and maximizing ROI. But when agencies ask clients for access to audience data for retargeting, concerns inevitably arise around privacy. Questions about how audience data is shared, secured, and used by social media giants like Meta and Google and whether users must be informed or give additional consent are now top of mind. 

If you’re a marketing leader, agency, or founder in the US or UK, this blog unpacks the evolving landscape of data privacy policies for retargeting on Meta and Google advertising platforms. You will gain clarity on what data is shared, how it’s protected, how these platforms use it, and obligations around privacy disclosures and consent. We’ll also explore real-life examples of how leading companies handle these issues and provide actionable guidelines for marketers to safely leverage customer data in compliance with privacy laws and platform policies. 

What Data Is Shared for Retargeting?

When clients provide audience data for retargeting, this typically involves customer contact information such as email addresses and phone numbers, online identifiers like cookies or mobile ad IDs, and engagement signals from websites or apps. For example, Meta’s Custom Audiences rely on hashed customer lists uploaded securely to match users on Facebook and Instagram. Similarly, Google Ads uses Customer Match lists for targeting.

This data represents a direct link between your offline or first-party customer information and the digital platforms’ user base, enabling precise ad targeting and suppression.

How Is This Data Shared and Secured?

When you upload customer data to Meta or Google for retargeting, the data is first encrypted and protected using secure processes. Before sending, the data is converted into a coded format called “hashed” data, which looks like a random string of letters and numbers. This means the platforms cannot see the actual personal details you shared. On their side, they use advanced technology to keep this data safe while matching it with their users.

But the responsibility doesn’t stop there. Marketers must keep the data clean and safe, make sure only authorized people can access it, and regularly check for any risks or leaks. Both Meta and Google strongly advise uploading data only from customers who have clearly agreed to share their information. This helps add an extra layer of privacy protection.

How Do Meta and Google Use This Data?

Meta and Google use audience data shared by marketers to match customers with their respective users on social networks or ad inventories. This enables an advertiser’s retargeting campaigns, lookalike audience creation, and customer suppression lists to work effectively. Both platforms emphasize transparency and user control users can manage or opt out of personalized ads on these platforms.

Recent updates in 2025 have introduced tighter restrictions, such as Meta limiting “overly personalized” targeting and requiring businesses to clearly disclose and obtain consent for data use in advertising. Google introduced a 540-day cap on Customer Match list durations, encouraging advertisers to maintain fresh and compliant data sets.

Privacy Concerns for Organizations

Privacy concerns run deep both from a regulatory and reputational perspective. Companies must ensure compliance with:

GDPR in the UK/EU: mandates explicit user consent and rights to access, rectify or erase personal data.

CCPA in the US: provides consumers transparency and opt-out rights regarding personal data collection and sharing.

PECR and ePrivacy Directive (UK): governs electronic marketing communications, requiring lawful basis and explicit consent for unsolicited marketing.

Failing to comply can result in fines, legal risks, and loss of customer trust.

Privacy Wording and Terms Organizations Should Include

Clear, transparent privacy policies must explain: 

  • What data is collected and for what purpose, including retargeting and lookalike creation. 

  • How data is shared with Meta, Google, or other third parties for advertising. 

  • The lawful basis for processing (e.g., explicit consent). 

  • User rights to withdraw consent or opt out of targeted advertising. 

  • Data retention periods and security measures. 

Updating opt-in forms and consent management tools to reflect these needs is critical in 2025 and beyond.

What Marketers Should Confirm Before Sharing Data for Retargeting

Before you upload any customer list to Meta Custom Audiences or Google Customer Match, marketing leaders should align with their data, legal and privacy teams on a few non negotiable points: 

  1. Legal basis and consent coverage

    • Do we have a clear legal basis for using this data for advertising under GDPR or CCPA, usually explicit consent or a documented legitimate interest? 

     

    • Have customers been told, in plain language, that their data may be used on platforms like Meta and Google for retargeting and lookalike audiences?

       

  2. Allowed identifiers and data minimisation

    • Are we only sharing the minimum fields needed, such as email, phone or hashed identifiers, and not any sensitive categories like health status, exact financial data or other protected attributes that Meta and Google restrict?  

     

    • Can any fields that are not required for matching be removed or anonymised before upload?

       

  3. Data quality, freshness and retention limits

     

    • Is the list reasonably fresh and cleaned for bounces and unsubscribes?

       

    • Do we regularly refresh our Google Customer Match lists so they stay within the 540-day limit and don’t include outdated or non-compliant contacts? 

     

  4. Internal access controls and secure handling

     

    • Who within the company has the ability to export, transform, and upload customer data to advertising platforms?

       

    • Are uploads done using approved secure channels, with hashing applied before or during upload according to platform guidance? 

       

    • Do we log which lists were uploaded, by whom and for which campaigns?

       

  5. Up to date platform terms and product features

     

    • Have we reviewed the latest Custom Audience and Customer Match terms, including restrictions on sensitive categories, special ad categories and new product features like consent mode or AI personalisation that may affect how data is used? 
       
    • Are our privacy notices aligned with the way Meta and Google actually process the data today, not how they worked two years ago?

       

  6. User rights and opt out mechanisms

     

    • Do we have a clear and simple way for customers to opt out of retargeting or withdraw consent, and do those choices flow through into our CRM and audience lists?

       

    • Are we prepared to respond if a user asks what data we hold on them and how it is used for advertising?

       

By walking through this checklist with their internal stakeholders, marketers can make informed decisions about when and how to share customer data with Meta and Google, instead of treating retargeting uploads as a purely tactical step in campaign setup.

Retargeting Data Privacy Handling Updates

In the last few years, both Meta and Google have tightened how customer data can be used for retargeting and audience building. A few key updates matter directly to marketing leaders: 

Meta custom audience consent requirements

Meta has increased its focus on consent and lawful data use. Advertisers using Custom Audiences must be able to prove that the people in their lists have been informed and have agreed to their data being used for advertising. Brands are expected to certify compliance when uploading audiences and to avoid using data that could reveal sensitive attributes such as health, financial status or other protected characteristics.

Meta restrictions on sensitive custom audiences and conversions

From 2 September 2025, Meta is rolling out proactive restrictions on certain custom audiences and custom conversions that may suggest non permitted sensitive information. Audiences or events that are flagged can be limited or disabled. This makes it even more important that marketers exclude sensitive fields at the source and align targeting with allowed categories.

Google’s Customer Match retention limit of 540 days

Starting 7 April 2025, Customer Match lists in Google Ads and Display and Video 360 have a maximum membership duration of 540 days. Any user record older than that is no longer eligible, so advertisers must refresh lists regularly and keep only up to date, consented contacts in their retargeting pools.

Conclusion: A Thought Leader’s POV on Customer Data Sharing

For marketing leaders debating whether to share customer data for lookalike targeting or suppression, the answer is yes, but only with rigorous privacy governance and transparent user communication. Platforms like Meta and Google provide advanced security and compliance frameworks, but the burden of consent collection, disclosure, and data stewardship sits squarely with the marketer.

By embedding clear privacy disclosures, continuously auditing data practices, and respecting user rights under GDPR and CCPA, marketing teams can confidently harness the power of retargeting without compromising trust or compliance. Thoughtful, ethical data sharing is today’s competitive advantage in the digital marketing landscape.

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