Cookieless advertising

The future of third-party cookies was up in the air for quite a long time. And while we now know they won’t be completely deprecated, it can’t be denied that their quality continues to decay, with at least 55% of people rejecting cookie tracking As the online advertising ecosystem slowly weans itself from this decades-old foundation of digital advertising, marketers now face a key challenge: how to target the right audience and measure performance without compromising user privacy or ROI.

In this article, we break down what’s driving the shift away from cookies, explore all viable alternatives, and provide practical guidance on how to advertise without cookies. Whether you’re just starting to plan or already testing solutions, you’ll find clear steps to future-proof your advertising strategy.

Why are third-party cookies going away?

Third-party cookies are no longer as widely used due to rising privacy concerns and regulatory pressure. Because they allow advertisers to track users across multiple websites and predict user behavior without meaningful consent, third-party cookies fuel growing concerns about surveillance, the ethics of tracking user behavior, and data misuse.

As a counter to this, governments have introduced strict data privacy laws like GDPR and CCPA. At the same time, users are demanding more transparency and control over how their data is tracked across the web. Major web browsers (e.g. Safari and Firefox) have also stepped in and are responding by phasing out support for third-party cookies with the goal of reducing cross-site tracking and protecting individual user data.

The result? Advertisers can increasingly no longer rely on cross-site tracking to identify users, retarget them, or measure campaign success. That’s a major shift — but also an opportunity to rebuild trust and performance with more transparent, privacy-first strategies.

There are two main ways advertisers are likely to be affected by this change: How they target audiences with personalized ads and the measurement and attribution of their ad efforts. When combined, both contribute to overall ad performance and ROI, so the next section will discuss how to pick up where third-party data leaves off.

What will replace cookie-based advertising?

There is no one-size-fits-all replacement for third-party cookies. Instead, advertisers are turning to a range of solutions, each with its own strengths and weaknesses.

Solutions will be suitable to different degrees depending on your brand’s goals. We’ll break down the most popular ones and how they weigh in on the factors listed in the previous section (targeting and personalization + measurement and attribution), as well as what type of audiences they are best suited for (new vs. existing).

In this section, we’re only discussing open internet inventories outside walled gardens, like CTV and other premium digital inventories here, as we’re assuming your brand wants to reach consumers where they spend 66% of their online time.

Contextual advertising

If you know your audience quite well, contextual advertising or buying audience segments from a publisher can be good ways to reach them (both to retain/upsell existing customers or acquire new ones) — if not the most precise. It can also be difficult to measure and attribute ad ROI using these methods. And if your goal is to reach new customers, you might not know their interests well enough yet to buy the right context or segment where they spend their time.

Pros:

• Doesn’t rely on tracking users
• Fully privacy-compliant

Cons:

• Less precise than behavioral targeting
• Doesn’t support retargeting

Example: Placing ads for running shoes on fitness blogs.

Best for: Awareness campaigns or advertisers with content-rich categories.

Watch out for: Matching ad creative to context is critical—irrelevant pairings can hurt performance.

First-party data strategies

First-party data — which refers to the data your brand collects directly from your own customers — can address numerous gaps left by walled gardens and contextual advertising. This first-party data provides the most precise foundation for targeting, as it offers insights into the genuine behaviors, preferences, and interactions of your established audience.

However, the data on its own isn’t all that’s needed to get going. Tools that enable collaboration on first-party data and ways to activate it are an essential part of this type of strategy. A primary example of this is a data clean room, which enables data collaboration from different players within the advertising ecosystem and — in some platforms — enables those insights from the collaboration to be activated directly with the chosen publisher. 

Pros:

• High-quality, consent-based data
• Privacy-compliant
• Useful for personalisation and measurement

Cons:

• Can take time to get all your proprietary data in place (although working with partners is also an option to supplement or enrich existing first-party data)
• Requires robust infrastructure to collect and manage

Example: Retailers using loyalty programs to collect customer emails and purchase history.

Best for: Advertisers prioritizing accuracy, compliance, and partnership with premium publishers.

Watch out for: Ensure the tools you use enable you to adhere to the compliance regulations that apply to your region or industry.

“[T]he quality and sophistication of first-party data have surpassed that of third-party data, offering advertisers a more precise and reliable foundation for their ad targeting strategies.” — Kim Engels, CEO, Converto AG

Google’s Privacy Sandbox

To avoid leaving marketers in the lurch, Google has introduced the Privacy Sandbox, consisting of several new APIs and functionalities added to the Chrome browser.

While there are too many of these to dive into them all here, there are two that the company itself has deemed relevant for targeting content and ads: The Topics API and Protected Audience API. Read our article for a full breakdown of the Privacy Sandbox APIs.

These APIs run locally on the user’s device, within the browser, and are designed to avoid sending raw user data to external ad platforms — instead enabling targeting through on-device processing.

What’s important to keep in mind is that — while privacy-preserving in their approach — targeting solutions tied to a user’s browser, rather than a persistent identity, poses challenges in frequency management, cross-device attribution, and reach optimization. These browser-based models can’t always distinguish between users or devices accurately, which impacts campaign efficiency.

‍Pros:

• Not shared with third parties

Cons:

• Offer limited capabilities to prospect for new customers
• Restricted to targeting Chrome users

Example: Targeting users interested in “travel” based on recent browsing topics.

Best for: Broad-reach campaigns within the Google ecosystem.

Watch out for: Low granularity and dependence on Google-defined topics.

First-party data isn’t optional anymore

First-party data is any information you collect directly from your customers — through website activity, app interactions, or purchases. It’s gathered with consent, often via a clear value exchange (like newsletter signups or exclusive offers).

In a cookieless world, first-party data utilization is the cornerstone of any successful digital advertising strategy. Its use not only strengthens targeting precision but also simplifies compliance, since the data is collected directly with consent. The integration of this owned data into advertising platforms can unlock more efficient segmentation, personalization, accurate measurement, and ongoing customer engagement.
In fact, first-party data is considered the most critical personalization tool by 78% of businesses.
Its growing role in modern advertising cannot be overstated:

• Targeting: First-party data lets you reach users based on real interactions with your brand, increasing relevance and conversion rates. It allows for more nuanced segmentation and lookalike modeling within privacy-compliant environments.

• Measurement: It provides a reliable foundation for performance tracking, attribution, and campaign optimization. Platforms like data clean rooms make it possible to measure cross-channel lift and user engagement without direct identifiers.

• Personalisation: Knowing who your users are helps tailor content, offers, and experiences that boost engagement. From dynamic email content to personalized landing pages, first-party data powers relevance.

• Customer expectations: Users increasingly expect personalised, relevant experiences—but only if their data is handled transparently and ethically. Brands seen as respectful stewards of data can build stronger long-term loyalty.

Already now, 54% of brands rely exclusively on first-party data for personalization, citing its higher quality. Another 39% say they prefer it because it’s easier to manage, as it’s data they own. (Statista)

"The advertising industry is realizing that first-party data isn’t just a fallback — it’s a strategic advantage.” — Bettina Schatz, Team Coordinator for Sales Growth, Data Advertising, and Market Analysis at willhaben

To maximize value, brands must ensure robust data integration processes — combining web, app, CRM, and offline data — to create a unified customer view. This positions advertisers to activate insights at scale while maintaining control over their most valuable asset: their own data. We’ll elaborate more on the how-to process in the following section.

How to plan a cookieless advertising strategy

Here are five practical steps to help advertisers transition smoothly to audience targeting without cookies — while maintaining performance and privacy compliance. 

Audit your current use of third-party cookies

Map where and how third-party cookies are used across your ad campaigns, platforms, and measurement systems.

Map your audience targeting and measurement dependencies

Understand which parts of your marketing strategy rely on third-party data, and which can be replaced.

Expand consented first-party data collection

Improve your first-party data collection by offering clear value to users (e.g. exclusive content, early access, discounts). Use value exchange tactics to collect first-party data in compliant, user-friendly ways.

Implement tools that let you collaborate on and activate first-party data

Collaborate on your first-party data with publishers, retailers, or independent data partners using privacy-first tools such as data clean rooms.

"The combination of ID-targeting methods and a data clean room approach meets the challenges of a future without third-party cookies head-on.”— Ilias Ntinas, D2C Analytics & Insights Manager at Samsung

Set KPIs and prepare for new measurement models

Accept that old attribution models may no longer work. Begin testing incrementality, modeled conversions, or clean room-based reporting. Redefine what success looks like in a cookieless landscape.

Test and measure performance

Run A/B tests across different targeting solutions to track performance, iterate, and improve.

Budget and media-mix reallocation strategies

The phase-out of third-party cookies is driving a measurable shift in digital advertising budgets. Channels that previously relied on cross-site tracking are declining in efficiency, prompting advertisers to rethink their advertising strategies, reassessing where and how media investments are allocated.

Emerging trends include:

• Increased investment in contextual advertising, as brands seek targeting methods that align with privacy standards while preserving relevance. Many are reallocating significant portions of their programmatic budgets toward contextual or semantic-based placements.
  
  
• Growth in first-party data environments, particularly connected TV (CTV), publisher direct buys, and in-app advertising. These environments offer both scale and control, making them attractive alternatives to third-party cookie–dependent inventory.
  
  
• Expansion of data collaboration strategies, including the use of clean rooms and identity-based solutions, to activate customer data securely across platforms and publishers.
  
  
• Dedicated testing budgets, with a growing number of advertisers setting aside spend to evaluate performance across emerging approaches.
  
  

While earlier sections of this article focused on open internet environments, it’s important to acknowledge that walled gardens (e.g. Google, Meta, Amazon, TikTok) are still capturing a significant share of reallocated ad spend. Platforms like Google Ads benefit from vast, consented first-party datasets and native targeting tools that are largely insulated from third-party cookie deprecation.

However, this scale comes with trade-offs. Walled gardens offer limited transparency and require advertisers' trust that their data will be handled in a privacy-preserving way. For advertisers seeking to unify customer insights across ecosystems, this makes data clean rooms and interoperable solutions even more critical. These platforms offer functionality like direct publisher integrations, real-time optimization, and more — without exposing user-level data.

Effective media reallocation doesn’t mean choosing one path. It means building a balanced strategy that spans high-quality open web inventory, emerging privacy-first tools, and selective use of closed ecosystems — always with an eye on data control, performance, and regulatory alignment.

Listen to a discussion of the typical journeys advertisers take when stepping away from their reliance on third-party cookies in Decentriq’s own podcast episode about the topic:

Case study: Prospecting without third-party cookies

The challenge:
Facing the decay of third-party cookie quality and the need to reach new prospective customers, a major Swiss bank sought to enhance its digital marketing strategy. The bank aimed to drive awareness and consideration across the Swiss market for a new product launch, requiring a solution that ensured user privacy and complied with stringent data regulations.

The Solution:
Collaborating with Goldbach, a premium publisher reaching approximately 90% of the Swiss population, the bank leveraged its first-party customer data to inform its targeting strategy. To maintain data privacy and compliance, the bank used Decentriq's Lookalike Clean Rooms, which employ AI to extend campaign reach beyond existing customer overlaps without exposing sensitive data. 

The Results:
Over a five-week campaign, the bank conducted an A/B test comparing Decentriq-generated audiences to traditionally purchased segments. The results were significant:

• 129% increase in click-through rate (CTR)
  
  
• 57% increase in page views
  
  
• 44% decrease in cost per page view

Read the full case study.

FAQs

What is cookieless advertising?

Cookieless advertising refers to targeting and measuring ads without relying on third-party cookies. It uses privacy-compliant alternative solutions like first-party data, contextual signals, or secure environments like data clean rooms.

Can you still target users without cookies?

Yes. You can target users using first-party data, contextual advertising, or up-and-coming solutions like Google’s Privacy Sandbox. The key is consent and compliance.

Is contextual advertising enough on its own?

Contextual advertising, also sometimes known as contextual targeting, is effective for awareness and broad targeting but lacks the precision of behavioral data. It works best when combined with other solutions that provide more specificity and thereby expanded targeting and personalization capabilities.

What tools do I need to go cookieless?

Key tools include consent management platforms, customer data platforms (CDPs), data clean rooms, and privacy-focused measurement solutions.

How do data clean rooms support advertising without cookies?

They allow advertisers to match first-party data with publisher audiences in a privacy-safe environment. No raw data is exchanged, and analysis is done in a secure, compliant way — making them ideal for targeting and measurement in a cookieless world.

Ready to rethink your ad strategy for a cookieless future?

Decentriq helps advertisers collaborate on and activate their first-party data in a privacy-safe, compliant environment — no third-party cookies needed. Our data clean rooms make it easy to collaborate with media partners, measure performance accurately, and stay ahead of privacy regulations.

Explore our advertiser data solutions.