The end of third-party cookies: what changes for marketing and how to prepare

For nearly thirty years, third-party cookies were the backbone of digital advertising. They allowed advertisers to track users across sites, personalize ads, measure conversions, and build segmented audiences with a precision that felt almost magical, but was actually a form of invisible surveillance.

In 2020, Google announced that Chrome would remove support for third-party cookies. The digital-advertising market panicked. Agencies, adtechs, and advertisers rushed to find alternatives. Then came postponements.

In 2025, Google fully ended Privacy Sandbox, its six-year attempt to create a replacement. The saga entered a new chapter: third-party cookies still exist, but the ground of digital advertising has changed forever.

If you work in marketing, media, or digital strategy, this article explains what really happened, what changes in practice, and how to build consumer intelligence that does not depend on future decisions by Google.

IN SUMMARY

Third-party cookies still exist in Chrome in 2026, but the scenario has changed irreversibly. Safari and Firefox have blocked them by default for years, users have more privacy controls, and strategies based only on third-party data became fragile.

What are third-party cookies, and why did they dominate digital marketing?

To understand what changes, it is important to understand what cookies do. First-party cookies are created by the site you visit. Third-party cookies are created by another domain and allow behavior to be tracked across different sites.

When you visit a shoe store and later see ads for that store across other platforms, that is third-party-cookie logic in action.

For digital marketing, this was transformative. It enabled precise targeting, cross-site conversion measurement, and retargeting at scale.

Attention point: the risk is not only that cookies may disappear tomorrow; the risk is continuing to allocate budget on a foundation that already has visible cracks.

The timeline: from announcement to retreat, and what remains

The story of third-party cookies over the last years is turbulent. Understanding it prevents teams from mistaking apparent stability for strategic safety.

The conclusion is simple: the issue is not only when cookies end in Chrome, but that depending on them as the only consumer-intelligence source is already unsustainable.

What changes in practice for digital marketing?

Google’s retreat did not restore the old status quo. The ecosystem changed structurally, and teams that treated the delay as a solved problem are building on a moving foundation.

Reduced audience coverage

With Safari and Firefox already blocking third-party cookies and more users adopting privacy restrictions, the real coverage of third-party audiences has consistently decreased.

Attribution and measurement with blind spots

Consumer journeys across devices and platforms now have relevant blind spots. Attribution models based on cross-site tracking lose precision where cookies do not reach.

Retargeting with fragmented reach

Retargeting depends on identifying users who visited a site but did not convert. With partial browser blocking, lists become smaller and cost per conversion rises.

Regulation is arriving with force

LGPD, GDPR, and similar regulations in many countries made user consent a legal requirement, not an optional preference.

Attention point: the risk is not only that cookies may disappear tomorrow; the risk is continuing to allocate budget on a foundation that already has visible cracks.

The alternatives: what replaces third-party cookies?

The good news is that the market did not stand still. A robust set of alternatives has been developed and tested. None replicate cookies exactly, but together they create a stronger and more ethical intelligence base.

1. First-party data

These are the data collected directly from the relationship between brand and consumer: registrations, purchase history, site behavior, e-mail and app interactions.

The challenge is that they require direct relationships, CRM discipline, loyalty strategies, content, and consistent data capture over time.

2. Second-party data

Second-party data are first-party data shared between partners with complementary interests and proper consent. They have less scale than third-party data but far more reliability.

3. Contextual targeting

Contextual targeting analyzes the content being consumed and serves ads relevant to that context, without individual tracking or privacy risk.

4. Identity solutions and clean rooms

Identity solutions based on authenticated data, such as hashed e-mail, allow audience matching without exposing personal data. Clean rooms enable joint analysis in secure environments.

5. Synthetic data and predictive personas

Synthetic data is the most advanced approach: instead of tracking real individuals, AI models build behavioral representations from aggregated and anonymized patterns.

The result is Synthetic Personas: profiles that simulate how real consumers think, decide, and react, available for consultation at any time and compatible with LGPD.

How to build a privacy-first marketing strategy

The goal is not to replace third-party cookies with a single alternative. It is to build a data and intelligence architecture that works with or without them.

1. Audit your current dependence on third-party cookies

Map which campaigns, audiences, and reports depend on third-party data today. This defines the real risk and the priority of actions.

1. Strengthen your first-party data base

Invest in strategies that encourage consumers to share data directly: loyalty programs, exclusive content, account-based personalization, and experiences that return value for data.

1. Implement consent strategically

Do not treat consent banners as bureaucracy. Treat consent as an opportunity to explain the value exchange and build trust.

1. Diversify your consumer-intelligence sources

Avoid concentrating all intelligence in one source. Combine first-party data, contextual targeting, social listening, and predictive intelligence based on synthetic data.

1. Test and measure in an environment with and without cookies

Configure analytics and attribution to work even when third-party cookies are unavailable, using first-party models, server-side tracking, and probabilistic measurement where needed.

Why synthetic data is the most robust answer for cookieless marketing

Among all alternatives, synthetic data and Synthetic Personas offer the most complete capability set for replacing the intelligence once provided by third-party cookies.

While the market debates whether cookies end tomorrow or in two years, companies using synthetic-data intelligence already operate independently of that variable.

What to expect in the coming years: regulation, user control, and the new privacy standard

Even without a definitive deadline in Chrome, the direction of the industry is clear and irreversible.

User control as the standard, not the exception

Google kept cookies in Chrome, but committed to expanding user privacy controls. The global trend is toward more control and less invisible tracking.

Growing regulation in Brazil and worldwide

LGPD in Brazil is only the beginning. Privacy regulation is expanding globally, and consent plus data minimization will become stricter.

AI as a structural replacement for tracking

AI is creating alternatives that make individual tracking unnecessary. Behavioral models trained on aggregated data can predict behavior without privacy risk.

Consolidation around first-party data and synthetic data

The market is converging toward a model where direct consumer relationships and intelligence built on owned or synthetic data define competitive advantage.

Frequently asked questions about the end of third-party cookies

We separated some of the most common questions our clients ask.

What replaces third-party cookies in digital marketing?

The main alternatives are first-party data, contextual targeting, authenticated identity solutions, clean rooms, and synthetic data with Synthetic Personas.

Will third-party cookies disappear in Brazil?

In Chrome, there is no definitive deadline, but Safari and Firefox already block third-party cookies by default. The strategic dependency is the real risk.

What is first-party data?

First-party data are collected directly through the relationship between brand and consumer, with explicit consent. They include registrations, purchases, site behavior, and e-mail or app interactions.

What was Google’s Privacy Sandbox?

Privacy Sandbox was Google’s project to create privacy-preserving alternatives to third-party cookies. After years of development, low adoption, and regulatory pressure, it was discontinued.

How does LGPD affect third-party cookie use in Brazil?

LGPD requires an adequate legal basis, usually explicit and informed consent, for collecting and using personal data through cookies.

This section explains how marketers can reduce dependence on third-party tracking and build a privacy-first consumer-intelligence model.