This comprehensive analysis examines the critical distinctions between first-party and third-party cookies, their technological foundations, privacy implications, regulatory frameworks, and the evolving landscape of cookie-based tracking in digital advertising. First-party cookies are created directly by the websites users visit and enable essential functionality like maintaining login sessions and shopping cart persistence, while third-party cookies are placed by external advertisers and analytics providers to track user behavior across multiple websites for targeted advertising purposes. The distinction between these cookie types has become increasingly important as browsers have begun blocking third-party cookies by default, regulatory bodies have implemented stringent privacy laws, and the digital advertising industry faces a fundamental transformation away from cross-site tracking mechanisms. This report explores the technical mechanisms, privacy concerns, legal requirements, browser implementations, and emerging alternatives that characterize the current and future state of cookie-based tracking technology.
Foundational Understanding of Web Cookies and Their Purpose
The Evolution of Cookies in Digital Systems
Web cookies represent one of the most fundamental yet frequently misunderstood technologies on the modern internet. When the internet was in its earliest stages, cookies served a simple technical purpose as small packets of information transmitted between servers and browsers to facilitate basic program functionality. As the internet evolved from a collection of static documents to an interactive ecosystem of web applications and commercial platforms, cookies transformed into a sophisticated tracking infrastructure that underlies much of digital commerce and advertising. The original technical design of cookies was elegant in its simplicity—they allowed browsers to maintain state information across separate requests, solving a fundamental problem in stateless HTTP protocols where each request to a server had no inherent memory of previous interactions. However, this same mechanism that enabled convenient user experiences also created opportunities for surveillance and behavioral tracking that were not always transparent or consensual.
The emergence of commercial internet services in the 1990s and 2000s accelerated the adoption and sophistication of cookie technology. What began as a utility for remembering user preferences evolved into an infrastructure for tracking user movements across the web, building detailed profiles of consumer behavior, and enabling increasingly sophisticated targeting of advertisements. This transition from functional necessity to ubiquitous tracking mechanism occurred gradually, often without explicit user awareness or consent, creating the privacy tensions that now characterize cookie-related policy discussions. Early iterations of cookie standards like RFC 2109 and RFC 2965 recommended that browsers protect user privacy by not allowing cookie sharing between servers by default, but the later RFC 6265 standard released in April 2011 explicitly allowed user agents to implement whichever third-party cookie policy they wished, effectively opening the door to widespread cross-site tracking.
How Cookies Function in Modern Web Architecture
From a technical standpoint, cookies operate through a deceptively simple mechanism that has proven remarkably durable despite its original simplicity. When a user’s browser requests a resource from a web server, that server can instruct the browser to store a small text file containing specific data, typically up to 4 kilobytes in size. This stored file is then automatically transmitted back to the server with every subsequent request from the same browser, allowing the server to recognize and differentiate individual users based on unique identifiers stored within the cookie. The data contained within cookies can range from simple session identifiers to complex behavioral profiles, and the mechanism requires no additional user action once the cookie has been initially set.
The power of this simple mechanism lies in its invisibility and automaticity. Unlike other forms of data collection that might require explicit user action or notification, cookies operate silently in the background, continuously transmitting information about user behavior to remote servers. The browser handles this transmission automatically and completely, requiring no conscious awareness or input from the user. This technical reality creates a significant divergence between how users perceive cookie functionality and how cookies actually operate in practice, a gap that regulatory frameworks like GDPR and CCPA have attempted to address through requirements for explicit consent and transparency.
Technical Architecture and Creation Mechanisms
First-Party Cookie Creation and Architecture
First-party cookies are created and controlled directly by the website domain that the user is actively visiting, either through server-side code or JavaScript executing within the website itself. When a user navigates to a website like Amazon.com, that website’s servers can immediately create cookies that will be stored under the amazon.com domain, ensuring that only Amazon’s servers can subsequently read and modify these cookies. The technical creation process typically occurs through one of two mechanisms: either the website’s server includes a Set-Cookie header in its HTTP response to the browser, or JavaScript code executing within the webpage uses the document.cookie API to create cookies directly within the browser environment.
The scope and accessibility of first-party cookies is carefully controlled by browser security models to ensure that cookies created by one website cannot be accessed by other websites. This domain isolation principle represents a fundamental security boundary in web architecture, analogous to the separation of applications on a computer system. When a user visits example.com, cookies stored under the example.com domain will only be sent to example.com’s servers and will never be transmitted to requests destined for other websites. This architectural constraint means that first-party cookies can only be read by the website publisher that created them, and they can only be accessed when the user is actively visiting that specific website or its subdomains (depending on how the Domain attribute is configured).
First-party cookies typically fall into several functional categories that serve distinct purposes within website operations. Session management cookies maintain information about a user’s current browsing session, including login status, items in a shopping cart, and temporary user preferences that persist only for the duration of that session. Personalization cookies remember user preferences such as language settings, display themes, interface layout preferences, and other customization options that enhance usability across multiple visits. Strictly necessary cookies perform essential functions required for the website to operate properly, such as maintaining security, preventing fraud, or enabling basic functionality that users have explicitly requested. These strictly necessary cookies are often exempt from explicit consent requirements under privacy regulations because they are considered essential for contract performance or legitimate interests in security.
Third-Party Cookie Creation and Cross-Site Mechanism
Third-party cookies operate through a fundamentally different mechanism that enables tracking and data collection across multiple websites and domains. Unlike first-party cookies that are created directly by the website a user is visiting, third-party cookies are created by external servers—typically advertising networks, analytics providers, or other data collection services—through code embedded within websites. The creation mechanism typically begins when a website incorporates a script tag or embed code from an external service provider into its own HTML. This embedded code instructs the browser to request resources from the third-party server’s domain, and when that request is fulfilled, the third-party server can include Set-Cookie headers in its response, causing the browser to store cookies under the third-party domain rather than the website domain the user is actually visiting.
A concrete example illustrates this mechanism clearly. When a user visits sunglassesstore.com, that website may include an embedded script from an advertising network like ad.foxytracking.com. When the browser executes this script, it automatically requests resources from ad.foxytracking.com, and in response, the advertising network sets a cookie under the ad.foxytracking.com domain. Later, when the same user visits newswebsite.com, which also includes code from the same advertising network, the browser automatically sends that existing ad.foxytracking.com cookie to the advertising network’s servers as part of the request for resources from newswebsite.com. This mechanism allows the advertising network to recognize the same user across multiple websites and correlate their behavior across these different domains, creating a cross-site profile of the user’s interests and browsing patterns.
The technical architecture enabling third-party cookies is built into the fundamental HTTP protocol design, which automatically transmits cookies to their origin domain whenever the browser makes any request to that domain, regardless of which website initiated the request. This automatic transmission mechanism, while useful for legitimate purposes like authentication across services, has been repurposed for extensive cross-site tracking that most users do not fully understand or consent to. As of 2014, some websites contained cookies from over 100 different third-party domains, with websites setting an average of 10 cookies but reaching maximum numbers exceeding 800 cookies in extreme cases. This proliferation of third-party cookies has created what researchers describe as an ecology of invisible tracking, where users have no direct relationship with most entities collecting data about their behavior.
Comparative Analysis of Cookie Types and Their Functions
Origin and Creation Authority
The most fundamental distinction between first-party and third-party cookies lies in who controls their creation and operation. First-party cookies are created exclusively by the website domain that appears in the browser’s address bar—the website the user deliberately chose to visit and is consciously interacting with. This direct relationship between the website the user is visiting and the entity creating the cookie creates a conceptual and practical basis for considering these cookies as part of the service agreement between user and website. The user has chosen to visit amazon.com, and Amazon creates cookies to enhance that experience; this represents a direct contractual relationship.
Third-party cookies, by contrast, are created by external domains that the user has not deliberately visited and often has no direct relationship with. These external entities—advertising networks, data brokers, tracking platforms, social media networks—gain the ability to track user behavior across the web through code that website publishers have chosen to embed within their pages. The user visits newswebsite.com to read an article, but Google’s advertising network or Facebook’s tracking pixel simultaneously creates and maintains cookies that track their behavior across multiple websites without their conscious participation. This asymmetry in awareness and consent represents a core privacy concern that has driven regulatory scrutiny and consumer activism against third-party cookies.
Scope of Access and Cross-Site Tracking Capability
The technical scope of access represents another critical distinction between these cookie types. First-party cookies are restricted to the domain that created them and are only accessible to that domain’s servers; Amazon’s cookies cannot be read by Google, nor can they be transmitted to any domain other than amazon.com. This domain isolation creates a fundamental limitation on the reach of first-party cookies—they can only accumulate information about user behavior specifically on the website that created them. Even if a website uses first-party cookies for behavioral tracking or analytics, those cookies can only track that user’s activity on that specific website; they cannot see what the user does on other websites.
Third-party cookies, by virtue of their cross-site accessibility, enable the accumulation of data across multiple websites into a unified profile maintained by the third-party service provider. Because third-party cookies are accessible to the third-party domain from any website that includes the third-party’s tracking code, a single advertising network can see a user’s behavior across hundreds or thousands of websites. This cross-site tracking capability is the fundamental feature that makes third-party cookies valuable for behavioral advertising, as it enables advertisers to build detailed profiles of user interests, demographics, and purchasing intent across the entire web. However, this same capability represents the core privacy invasion that critics and regulators have identified as problematic.
Data Storage and Persistence Characteristics
First-party and third-party cookies also differ in their typical persistence characteristics and the types of data they store. First-party cookies typically store information that is directly relevant to the user’s experience on that specific website—login credentials (or more commonly, session tokens that prove authentication), shopping cart contents, language preferences, accessibility settings, and behavioral signals that help personalize content on that site. The data stored in first-party cookies is generally limited to information that the user has explicitly provided to the website through forms, selections, or interactions, or information about their behavior on that specific website.
Third-party cookies store different types of data with different purposes and implications. They typically store identifiers that allow the third-party service to recognize the user across websites, along with behavioral signals inferred from observing that user’s browsing activity across multiple websites. Advertising networks store data about which websites the user has visited, what products they have viewed, which advertisements they have been shown and clicked on, what searches they have performed, and inferred demographic and psychographic characteristics based on these behavioral patterns. The data accumulated in third-party cookies often becomes quite intimate and sensitive, potentially including information about health interests, financial situations, political preferences, and other sensitive categories that users might not consciously realize they are revealing.
| Characteristic | First-Party Cookies | Third-Party Cookies |
|—|—|—|
| Origin | Website being visited | External advertising/tracking domain |
| Accessibility | Only by the website that created them | Accessible to third-party from any website embedding their code |
| Scope | Limited to single website behavior | Cross-site tracking across multiple websites |
| Data Type | User preferences, login info, shopping cart | Behavioral profiles, interests, demographics |
| User Awareness | Generally higher (more obvious) | Typically hidden from user awareness |
| Privacy Concern | Lower; user typically consents implicitly | High; often without user knowledge or consent |
| Browser Handling | Allowed by default in all browsers | Increasingly blocked by default in major browsers |
Privacy and Security Implications
The Privacy Concerns Associated with Third-Party Tracking
The proliferation of third-party cookies has created an extensive infrastructure of behavioral tracking that represents a fundamental challenge to online privacy. The Cambridge Analytica scandal, which revealed how detailed user data harvested through Facebook and other platforms was used to influence political behavior, crystallized public awareness of how aggregated behavioral data could be weaponized for manipulation. This scandal demonstrated that the seemingly abstract data collected through cookies and similar tracking mechanisms could be correlated back to individuals and used to target them with manipulative content designed to influence their political and consumer behavior. Following this scandal, public opinion shifted noticeably toward viewing behavioral tracking as a significant privacy invasion worthy of regulatory intervention.
The privacy concern with third-party cookies extends beyond simple observation to the creation of detailed predictive profiles. Through the accumulation of data about which websites a user visits, what products they search for, what content they consume, and what advertisements they click on, data brokers and advertising networks can infer sensitive information about users’ financial situations, health conditions, political beliefs, sexual orientation, and other intimate characteristics. Users rarely understand the full extent of this data collection or its sensitivity, often thinking of browsing behavior as innocuous when the aggregated patterns can actually reveal profound personal information. The ability to re-identify supposedly anonymous data by correlating it with other data sources means that privacy can be compromised even when explicit identifiers are not directly collected.
The lack of transparency surrounding third-party cookie tracking represents a significant component of the privacy concern. Most users have limited visibility into which third-party trackers are monitoring their activity or what data those trackers are collecting. The typical user cannot easily identify which cookies on their device are third-party tracking cookies, what data they contain, or which external entities have access to their behavioral profiles. This opacity means that users cannot make informed decisions about their privacy or take meaningful action to protect it, creating an asymmetry of information and power between individuals and tracking companies.
Security Vulnerabilities and Malicious Use
Beyond privacy concerns, third-party cookies create security vulnerabilities that can be exploited by malicious actors. Because third-party cookies are stored with other browser data and are automatically transmitted with requests, they can be intercepted by attackers on unsecured networks. If a user connects to public Wi-Fi and websites transmit sensitive information through cookies over unencrypted HTTP connections, attackers on the same network can potentially intercept and exploit these cookies. Even more concerning, attackers can create malicious cookies disguised as legitimate tracking cookies that contain malware or redirect users to phishing sites.
Session hijacking represents another significant security concern related to cookies. If an attacker can steal a session cookie containing authentication credentials or session identifiers, they can impersonate the user to that website, potentially gaining unauthorized access to sensitive accounts like banking or email. Third-party cookies increase this risk because they are transmitted across more networks and stored in browsers alongside numerous other cookies from unknown sources, creating more opportunities for interception or theft. The proliferation of cookies means that browsers accumulate hundreds of cookies from various domains, and users have limited ability to audit or remove potentially compromised cookies.
Zombie cookies represent a particularly insidious category of tracking cookie that combines persistence with evasion capabilities. Unlike standard cookies that can be deleted by users, zombie cookies store backup copies in multiple locations and can recreate themselves even after deletion attempts. This persistence enables trackers to maintain identification of users despite their efforts to clear cookies, creating a form of surveillance that resists user attempts at privacy protection. Zombie cookies employ techniques like cookie syncing to link user identifiers across multiple tracking platforms, creating comprehensive cross-platform profiles.
Protection Mechanisms and Best Practices
Recognizing these privacy and security concerns, security experts and privacy advocates recommend multiple protective measures at both the user and website levels. For website developers, implementing security best practices for cookie handling involves using appropriate cookie attributes to restrict their scope and transmission. The Secure attribute ensures cookies are only transmitted over HTTPS connections, preventing them from being intercepted over unencrypted HTTP connections. The HttpOnly attribute prevents cookies from being accessed through JavaScript, significantly reducing the risk of cookie theft through cross-site scripting (XSS) attacks.
The SameSite attribute provides protection against cross-site request forgery (CSRF) attacks by controlling whether cookies are transmitted with cross-site requests. When set to Strict mode, cookies are never sent with cross-site requests, providing strong protection but potentially breaking some legitimate cross-site functionality. Lax mode, the default setting for most modern browsers, represents a compromise that allows cookies to be sent for top-level navigations and same-site requests but prevents transmission with embedded resources like images or iframes from other sites. Cookie prefixes like __Host- and __Secure- provide additional protection by restricting where cookies can be set and from which origins.
At the user level, multiple protective approaches are available. Enabling enhanced tracking protection in browsers like Firefox and Safari automatically blocks many known third-party trackers and cookies from setting themselves. Using browser extensions specifically designed to block tracking cookies and advertisers provides additional protection beyond browser defaults. Regularly clearing cookies and browser cache removes accumulated tracking data, though this must be done repeatedly as new cookies are created with each browsing session. Using privacy-focused browsers like Brave and DuckDuckGo that have tracking blocking built into their core architecture provides comprehensive protection without requiring ongoing user action.
The Evolving Regulatory and Legal Landscape
European Union Framework: GDPR and ePrivacy Directive
The European Union has been among the most aggressive jurisdictions in implementing regulatory frameworks that constrain cookie usage and require user consent for tracking. The General Data Protection Regulation (GDPR), which came into effect on May 25, 2018, established comprehensive requirements for the collection and processing of personal data, and European regulators have explicitly applied these requirements to cookie-based tracking. Under GDPR principles, cookies that collect or transmit personal data are considered data processing activities that require a lawful basis and, typically, explicit user consent. The ePrivacy Directive, which predates GDPR, specifically requires informed consent before storing cookies on user devices except for strictly necessary cookies required for service operation.
The practical implementation of these European requirements has profoundly reshaped web design, leading to the ubiquity of cookie consent banners that now appear on the vast majority of websites visited by European users. These consent mechanisms must meet specific requirements to be considered valid under European law: consent must be freely given, specific, informed, and unambiguous, typically expressed through a clear affirmative action like clicking an “Accept” button. The Working Party 29 (now the European Data Protection Board) has clarified that consent cannot be obtained through pre-checked boxes, cookie walls that prevent website access unless cookies are accepted, or implied consent through continued browsing or scrolling. Websites must provide granular consent options allowing users to accept or reject different categories of cookies separately, and they must make it as easy to withdraw consent as it was to give it initially.
The European regulatory approach has proven influential globally, with many non-European websites implementing GDPR-compliant consent mechanisms to comply with the extraterritorial scope of the regulation. GDPR explicitly applies to the processing of personal data of EU residents by any organization, regardless of where the organization is located. This has effectively made European privacy standards a de facto global standard for many websites, as implementing separate systems for European and non-European users would be economically inefficient.
California and United States Regulatory Landscape
The United States has adopted a more fragmented, sector-specific approach to privacy regulation compared to the European Union’s comprehensive framework. California’s Consumer Privacy Act (CCPA), which went into effect on January 1, 2020, represents the most comprehensive state-level privacy law and provides certain rights to California residents regarding their personal information. The CCPA requires businesses that collect personal information from California residents to disclose what categories of information they collect and how they use it, provide consumers with rights to access and delete their personal information, and allow consumers to opt out of the sale or sharing of their personal information. Unlike GDPR, the CCPA does not explicitly require consent for cookie usage, but it does require a “notice at collection” informing users about data collection, and it requires businesses to honor consumer opt-out requests.
California’s Privacy Rights Act (CPRA), which amended the CCPA effective January 1, 2023, expanded privacy protections further by providing additional rights including the right to correct inaccurate information and the right to limit use of sensitive personal information. The CCPA and CPRA apply to for-profit businesses that meet size thresholds: annual gross revenues over $25 million, buying or selling personal information of 100,000 or more California residents, or deriving 50 percent or more of revenue from selling or sharing personal information. Unlike GDPR, the CCPA and CPRA do not require consent before collecting data through cookies, but they do require transparency and opt-out mechanisms, representing a lighter regulatory touch than European requirements.
Other states have begun implementing their own privacy laws following California’s example, including Virginia’s Virginia Consumer Data Protection Act (VCDPA), creating an increasingly complex patchwork of state-level privacy requirements. This state-level fragmentation has created challenges for businesses required to comply with multiple different legal frameworks, each with varying definitions of personal information and different procedural requirements. Consequently, many businesses have opted to implement privacy practices that exceed the requirements of any single jurisdiction, effectively adopting the most stringent standards as the baseline for compliance.
Global Privacy Framework Expansion
Beyond North America and Europe, privacy regulations implementing cookie-related requirements have proliferated globally. Brazil’s Lei Geral de Proteção de Dados Pessoais (LGPD), widely described as the Brazilian GDPR, borrows heavily from European regulatory principles but with notable differences in definitions and processing legal bases. China’s Personal Information Protection Law (PIPL), which came into effect in November 2021, provides explicit requirements for cookie usage consent and implements particularly strict protections for sensitive categories of information like biometric data and data regarding minors under 14 years old. South Africa’s Protection of Personal Information Act (POPIA) treats cookies as personal information requiring explicit informed consent before use.
This global expansion of privacy regulation creates a powerful incentive structure encouraging businesses to implement privacy-protective practices exceeding even the strictest local requirements, as maintaining separate systems for different jurisdictions would be economically inefficient. Consequently, the GDPR’s high privacy standards have become a de facto global baseline influencing privacy practices beyond Europe. Companies complying with GDPR generally find themselves compliant with most other privacy regimes, though ongoing attention to jurisdiction-specific requirements remains necessary.
Browser Evolution and Tracking Prevention Mechanisms
Safari and Apple’s Intelligent Tracking Prevention
Apple has positioned itself as a privacy-focused technology company and has implemented increasingly sophisticated tracking prevention mechanisms in Safari, its web browser. Intelligent Tracking Prevention (ITP), introduced in Safari 11 and iOS 11, represents Apple’s technological approach to reducing cross-site tracking while attempting to preserve website functionality. ITP uses on-device machine learning to identify which domains are used for tracking purposes and then isolates and purges tracking data from those domains, preventing the accumulation of cross-site behavioral profiles. Critically, this tracking protection operates entirely on the device without transmitting user browsing history to Apple, preserving user privacy even from Apple itself.
ITP has evolved through multiple versions, each expanding its tracking prevention capabilities. ITP 2.0, released in 2018, expanded protections beyond cookies to include other tracking mechanisms and began blocking third-party cookies by default in Safari. Subsequent versions have further tightened protections, with ITP limiting the lifespan of cookies set through JavaScript (client-side) to seven days, effectively rendering many analytics and advertising cookies dysfunctional regardless of their expiration date settings. Apple’s approach in Safari has been to block third-party cookies completely by default with no exceptions, preventing cross-site tracking entirely rather than attempting to balance tracking and functionality.
This comprehensive approach to blocking third-party cookies in Safari represents a significant practical limitation for advertisers and analytics providers, as Safari commands a substantial market share particularly among affluent consumers using Apple devices. Publishers and advertisers relying on third-party cookies for measurement and targeting have been forced to develop alternative approaches or accept reduced functionality for Safari users. Apple’s strategy has been influential, with other browser developers viewing Safari’s successful blocking of third-party cookies without breaking website functionality as validation that deprecating these cookies is technically feasible.
Mozilla Firefox’s Enhanced Tracking Protection
Mozilla Firefox has implemented Enhanced Tracking Protection (ETP), a progressive tracking prevention approach that operates at several levels. In the default configuration, ETP blocks known third-party trackers based on blocklists of known tracking domains compiled by the Firefox team and third-party organizations. This approach differs from Apple’s machine learning method by relying on maintained lists of known trackers, providing reliable blocking without the computational overhead of on-device machine learning. Users can adjust their tracking protection level from “Standard” (default) to “Strict,” which blocks additional trackers and cookies, though at some risk of breaking website functionality.
Mozilla has complemented cookie blocking with Total Cookie Protection, a feature that isolates each website in its own “cookie jar,” preventing cookies set in one website context from being accessed by other websites. This approach differs fundamentally from blocking third-party cookies entirely; instead, it partitions cookies so that the third-party cookie set when visiting website A cannot be accessed when the same third-party code appears on website B. Total Cookie Protection by default prevents cross-site tracking while allowing legitimate third-party functionality like social media login buttons to continue working within their direct context. Mozilla has rolled out Total Cookie Protection as the default for all Firefox users worldwide, making it one of the most comprehensive default tracking protections available in a major browser.
Google Chrome and the Third-Party Cookie Saga
Google’s approach to third-party cookie deprecation represents one of the most complex and contested developments in cookie policy, marked by multiple announcements, delays, and ultimately a reversal of position. In January 2020, Google announced plans to phase out support for third-party cookies in Chrome within two years, representing a fundamental challenge to the current digital advertising model that depends heavily on cross-site tracking. This announcement, framed as a privacy enhancement, sparked intense debate in the advertising industry, as Chrome commands approximately 60 percent of browser market share globally, meaning Chrome’s deprecation of third-party cookies would effectively end their viability as a primary tracking mechanism.
The deprecation timeline repeatedly slipped, with Google citing regulatory considerations and industry readiness concerns as justifications for delays. In June 2021, Google announced a two-year delay, pushing the deprecation timeline from 2022 to 2024. However, in July 2024, Google surprised the industry by reversing course entirely, announcing that instead of deprecating third-party cookies unilaterally, Chrome would introduce a new feature called Tracking Protection that allows users to make an informed choice about whether to permit third-party cookies, with the ability to adjust this choice at any time. This reversal represented a significant victory for advertisers and publishers who had lobbied against complete third-party cookie deprecation, but it also created uncertainty about the future of privacy protections in the advertising ecosystem.
Google’s stated rationale for the reversal focused on user choice and regulatory concerns, particularly feedback from the UK’s Competition and Markets Authority (CMA) that expressed concerns about Google’s unilateral control over deprecation timelines and their potential anticompetitive implications. However, Google continues to invest in Privacy Sandbox technologies designed to provide privacy-preserving alternatives to third-party cookies, including APIs for interest-based targeting (Topics API), conversion measurement (Attribution Reporting API), and real-time bidding (Protected Audience API). These APIs are intended to enable targeted advertising and measurement while reducing reliance on cross-site tracking identifiers.
Other Browsers and Fragmented Implementation
Beyond Safari, Firefox, and Chrome, other browsers have taken varied approaches to third-party cookie handling. Microsoft Edge, being Chromium-based like Chrome, has generally followed similar policies but provides users with tracking prevention settings allowing them to adjust the level of tracking protection. Brave browser, positioned as a privacy-focused alternative to mainstream browsers, blocks third-party cookies by default along with all tracking and advertisements unless users explicitly whitelist specific sites. DuckDuckGo browser similarly prioritizes privacy by blocking trackers by default with minimal reliance on cookies.
This fragmented landscape of browser implementations creates challenges for website developers and advertisers who must account for varying levels of cookie functionality across browsers. Different browsers begin blocking cookies at different points, use different blocklists or detection mechanisms, and respect different user preferences regarding cookie handling. The result is that websites and advertising services cannot rely on consistent cookie functionality across browsers, forcing them to develop cookie-independent measurement and targeting approaches or accept functionality degradation for users in privacy-protective browsers.
Third-Party Cookie Status and Deprecation Trajectory
Current Market Reality and Browser Implementation Timeline
As of October 2025, the landscape of third-party cookie support has become increasingly fragmented, reflecting years of browser implementations and policy changes. Safari and iOS have completely blocked third-party cookies since 2020, eliminating this tracking mechanism for Apple users entirely. Firefox has implemented Total Cookie Protection by default for all users, effectively partitioning third-party cookies to prevent cross-site tracking while maintaining their technical viability within single-site contexts. Brave and other privacy-focused browsers have blocked third-party cookies entirely for several years. Microsoft Edge provides third-party cookie blocking options, though they are not enabled by default, allowing users to choose their level of tracking protection.
Chrome’s situation represents the most complex scenario, as Google’s July 2024 decision to retain third-party cookies rather than deprecating them completely means that third-party cookies continue to function by default in the world’s most widely used browser. However, Chrome’s Tracking Protection feature allows users to restrict third-party cookies if they choose, and the browser does restrict them in Incognito mode. This represents a shift in framing from a technical deprecation to a user choice model, where third-party cookies technically remain viable but users can opt out of being tracked through them. Early reports indicate that when given the choice, substantial numbers of users elect to restrict third-party cookies, suggesting that while technically available, third-party cookie effectiveness continues to decline even in browsers that permit them.
The practical impact of fragmented browser implementations is that third-party cookie effectiveness has declined substantially compared to even five years ago, when they worked universally across all browsers. Advertisers report significantly reduced reach and effectiveness when relying on third-party cookies, as they cannot track users in Safari, Firefox, or privacy-focused browsers, limiting their addressability to roughly Chrome users who have not opted into Tracking Protection plus a smaller share of Edge users. This technological reality has accelerated industry migration toward alternative tracking and measurement approaches despite third-party cookies technically remaining viable.
Technical and Regulatory Drivers of Deprecation
Multiple factors have driven the industry trend toward third-party cookie deprecation despite its clear business value for advertisers and platforms. Regulatory pressure from GDPR, CCPA, and other privacy laws implementing informed consent requirements has made obtaining valid consent for third-party cookie placement and data transmission increasingly difficult and expensive, creating legal risk and compliance burden. User activism against tracking and surveillance has created consumer pressure on browsers to provide stronger privacy protections, with browser companies responding to market demand by implementing blocking mechanisms. Privacy advocacy organizations have provided substantial public education about the invasiveness and risks of behavioral tracking, shifting public opinion and regulatory willingness to restrict tracking practices.
Competitive dynamics among browser companies have also contributed to deprecation momentum, as each browser company has attempted to differentiate itself through enhanced privacy protections, creating a race-to-the-top dynamic toward stronger tracking protection. Apple’s early and comprehensive blocking of third-party cookies in Safari demonstrated technical feasibility, providing proof-of-concept that websites continue to function normally even without third-party cookie access. This validation of feasibility removed a key industry argument against deprecation, shifting the debate from technical possibility to business impact.
Public relations considerations have also influenced privacy protection implementations, as browser companies have marketed privacy protections as consumer benefits, positioning themselves as privacy-protective alternatives to competitors perceived as overly permissive of tracking. Google’s initial announcement to deprecate third-party cookies, before its later reversal, was framed explicitly as a privacy protection for users, creating positive PR value despite industry opposition. This dynamic where privacy protection provides marketing differentiation has created incentives for browsers to implement increasingly aggressive tracking protections.
First-Party Data and Emerging Alternatives to Third-Party Cookies
The Strategic Importance of First-Party Data
As third-party cookies have become increasingly unavailable or unreliable, marketers and publishers have rapidly shifted focus toward collecting and leveraging first-party data—information collected directly from users through their interactions with owned properties. First-party data includes information that businesses collect directly through their websites, mobile applications, customer databases, email subscribers, loyalty program members, and other direct relationships. This data is considered more valuable than third-party data derived from behavioral tracking because it comes directly from customers, can be collected with explicit consent, and belongs entirely to the business that collects it rather than being mediated through third-party data brokers.
The strategic advantages of first-party data collection extend beyond simple privacy compliance. Businesses that develop robust first-party data strategies maintain greater control over their data, eliminating reliance on external platforms whose policies and algorithms can change unpredictably. First-party data tends to be more accurate and higher quality than inferred third-party data, as it comes directly from customers rather than being inferred through behavioral observation. Importantly, first-party data enables personalization and targeting without relying on any external tracking mechanisms, making it compatible with stringent privacy regulations and consumer privacy preferences.
Companies with strong first-party data collection capabilities have positioned themselves advantageously in the post-third-party cookie environment. Starbucks, Netflix, Spotify, and Amazon have built sophisticated first-party data collections through login requirements, account creation, purchase histories, and explicit user preference settings. These companies can target users based on their explicit accounts and historical behavior without requiring any third-party tracking, maintaining competitive advantages that resist regulatory pressure or browser blocking. Smaller businesses without existing customer databases have found first-party data collection more challenging, as they must develop mechanisms to encourage users to provide information voluntarily, creating competitive disadvantages compared to established platforms.
Zero-Party Data and Explicit User Consent Models
Beyond first-party data, marketing strategists have identified a new category of consumer data called zero-party data—information that customers intentionally and proactively share with brands about their preferences, interests, and needs. This terminology, coined by Forrester Research, describes data that customers voluntarily provide expecting personalized benefits in return, such as through surveys, preference centers, quizzes, or registration forms that request their preferences, interests, or shopping intentions. Zero-party data differs fundamentally from both first-party data inferred from observation and third-party data inferred from behavioral tracking; it represents explicit customer intent and preferences directly communicated to the business.
The value proposition of zero-party data collection depends entirely on perceived fairness and reciprocity in the data exchange. Customers provide this information voluntarily only when they perceive clear value in return, whether through personalized content recommendations, customized product selections, or tailored communication matching their stated preferences. If businesses collect zero-party data but fail to honor the stated preferences or derive value from them without providing promised benefits, customer trust erodes and willingness to provide additional zero-party data decreases. Successful zero-party data collection requires clear communication about how data will be used, rapid responsive personalization demonstrating that the data improves their experience, and transparent respect for preferences and privacy boundaries.
Companies like Business Development Bank of Canada employ zero-party data collection effectively through strategically placed surveys on website landing pages asking about customer goals, then immediately personalizing content based on stated responses. Clothing retailers use style preference surveys to match customers with products more likely to appeal to their stated preferences, improving both customer satisfaction and conversion rates. This approach creates a virtuous cycle where customers provide information expecting personalized benefits, receive personalization that improves their experience, and become more willing to provide additional information in future interactions.
Contextual Advertising and Privacy-Safe Targeting
Contextual advertising represents another significant alternative to behavioral targeting through third-party cookies, focusing on the relevance of content being consumed rather than user characteristics or browsing history. Rather than tracking what a user has done previously and inferring their interests, contextual advertising matches advertisements to the content a user is currently consuming, displaying ads relevant to the article, video, or page they are actively engaging with. A user reading an article about running shoes sees advertisements for running shoes and athletic apparel; a user watching a cooking video sees advertisements for kitchen equipment and ingredients. This relevance-based approach requires no cross-site tracking, no behavioral profile inference, and no third-party data collection.
The competitive advantages of contextual advertising in a post-third-party cookie world are substantial. Contextual advertising provides genuine relevance to users based on their immediate interests rather than inferred past behavior that may not reflect current needs or intentions. Users generally perceive contextual advertisements as less intrusive than behavioral advertisements, as contextual ads relate to content they explicitly chose to consume rather than following them across the internet based on past behavior. Contextual advertising is inherently privacy-protective, requiring no personal data collection or third-party tracking, making it naturally compliant with privacy regulations and consumer privacy preferences.
Studies indicate that contextual advertising achieves comparable performance metrics to behavioral advertising in many contexts, contradicting assumptions that behavioral targeting is inherently superior. As of recent data, 47 percent of US digital ad buyers report using or planning to use AI for contextual targeting, indicating substantial industry adoption of this privacy-safe approach. Advanced AI models can now analyze webpage content with sophisticated understanding, identifying nuanced themes and contexts that enable precise matching between advertisements and content relevance without any personal data collection. This technological advancement has made contextual advertising viable even for premium advertising contexts where only the most precisely targeted campaigns would previously achieve necessary performance thresholds.
Google’s Privacy Sandbox and Alternative APIs
Google’s Privacy Sandbox initiative represents the technology platform’s comprehensive effort to develop privacy-safe alternatives to third-party cookies that would enable continued advertising and personalization while reducing cross-site tracking. Rather than blocking third-party cookies entirely, Google is developing a suite of APIs that would enable specific advertising use cases without relying on cross-site user tracking identifiers. The Topics API classifies users into interest-based categories based on their browsing activity, then shares only these interest categories rather than their complete browsing history with advertisers. The Attribution Reporting API enables measurement of ad conversions without requiring cross-site tracking of individual users. The Protected Audience API enables contextually relevant advertising and remarketing without accessing cross-site user tracking data.
These Privacy Sandbox APIs are intended to provide privacy-preserving alternatives that enable advertisers to continue targeting and measuring campaigns while preventing detailed cross-site user tracking that raises privacy concerns. Early testing indicates these APIs can achieve advertising objectives with performance metrics approaching those of third-party cookie-based targeting, though often not quite reaching performance parity due to the additional privacy protections built into the design. However, Privacy Sandbox adoption has faced substantial industry headwinds, with advertising industry investment in the initiative declining and marketers questioning whether the APIs will prove effective enough to justify the migration effort.
Server-Side Tracking and Consent Management Evolution
Server-side tracking represents another emerging alternative to client-side third-party cookie tracking, shifting data processing and storage from the user’s browser to the business’s servers or a managed service provider’s infrastructure. Server-side tracking collects data on the business’s servers rather than relying on third-party JavaScript executing in the user’s browser, providing greater control over data security and privacy while improving website and application performance. This approach enables data collection and sharing with analytics and advertising platforms using the business’s own servers as intermediaries, rather than allowing external platforms to track users directly.
Server-side tracking provides multiple advantages for businesses transitioning away from third-party cookies. It enables collection of higher-quality raw data that external platforms typically do not expose to customers, allowing businesses to maintain greater understanding of their user data. It provides protection against third-party platform algorithm changes and policy shifts, maintaining business continuity as external platforms evolve their services. Most importantly, it enables data collection and personalization while complying with privacy regulations and consumer privacy preferences, as the business controls the entire data pipeline and can implement appropriate consent management and security measures.
Consent management platforms (CMPs) have evolved as critical infrastructure for managing cookie collection and privacy preferences in an increasingly regulated environment. These platforms provide cookie scanning technology to identify all cookies and tracking technologies on a website, provide users with granular consent options for different cookie categories, display cookie information in user-friendly formats, and store and audit consent records for regulatory compliance. CMPs like Cookiebot, OneTrust, CookieYes, and others have become essential for businesses managing compliance across multiple privacy jurisdictions with different regulatory requirements.
Practical Implications and Stakeholder Impacts
Challenges for Digital Advertising and Measurement
The ongoing transition away from third-party cookie dependency creates substantial challenges for digital advertising measurement and optimization. For decades, advertisers have relied on third-party cookies to track user behavior across websites, attributing conversions to specific campaigns and individual touchpoints through user journey tracking. Third-party cookies enabled return on ad spend (ROAS) measurement, allowing advertisers to understand which campaigns and keywords generated actual conversions and adjust budgets accordingly. The loss of third-party cookie functionality eliminates this tracking capability, making it difficult to understand which advertising efforts drive business results.
Research indicates that 69 percent of advertisers believe third-party cookie deprecation will affect their business more negatively than privacy regulations like GDPR and CCPA, reflecting deep concerns about measurement degradation. Marketing industry surveys show that fewer than 46 percent of businesses feel “very prepared” for marketing without third-party cookies, indicating widespread anxiety about upcoming changes. The most immediate impacts affect retargeting campaigns, which lose precision when third-party cookies cannot track users across websites to display ads for products they previously viewed. A/B testing becomes more difficult without third-party cookie-enabled attribution, as businesses struggle to isolate the effect of specific campaign variations. Frequency capping—preventing ad overexposure—becomes more difficult without cross-site tracking indicating how many times a specific user has been exposed to advertisements.
However, early evidence from companies adapting to first-party data approaches and alternative tracking methods suggests that sophisticated businesses can achieve comparable results through alternative methodologies. A Boston Consulting Group study found that large enterprises implementing cookieless strategies achieved 10 percent performance improvements, while small businesses achieved gains up to 100 percent, likely reflecting competitive advantages from early adoption and optimization of alternative approaches. These findings suggest that while the transition creates disruption, businesses investing in first-party data, contextual targeting, and alternative measurement approaches can maintain competitive effectiveness in a post-third-party cookie environment.
Impact on Publishers and Content Creators
Publishers and content creators face particular vulnerability to third-party cookie deprecation, as many rely heavily on advertising revenue and programmatic advertising powered by third-party cookie-based targeting. The loss of precise user targeting capability threatens to reduce advertising effectiveness and consequently reduce advertising prices and publisher revenue. Publishers who previously could offer highly targeted audiences to advertisers can no longer make these precision offers without access to third-party tracking data, forcing them to compete primarily on audience size and content relevance rather than targeting precision.
However, publishers also possess substantial first-party data advantages, particularly those with registered user bases and subscription services. Major publishers like The New York Times have developed sophisticated first-party data collection through registration systems that capture user information, location, interests, and reading behavior. This first-party data enables these publishers to offer advertisers access to precisely targeted audiences without requiring third-party cookies or reliance on external tracking platforms. Publishers without existing subscription or registration systems face greater challenges, but many are developing strategies to encourage user registration, email subscriptions, and loyalty programs that generate direct customer relationships and first-party data.
Consumer and User Experience Considerations
For consumers and end users, the transition away from third-party cookies presents mixed implications with both protective and potentially negative dimensions. On the protective side, reduced third-party cookie tracking decreases surveillance, makes users less vulnerable to manipulation through targeted disinformation, and reduces their exposure to targeted manipulation of consumer behavior for commercial or political purposes. Users gain greater privacy protection and reduced tracking regardless of technical competence, as browsers provide default protections without requiring conscious user action.
However, consumers may experience reduced advertising relevance and increased exposure to irrelevant advertisements that fail to match their interests or needs. With third-party cookies unavailable and many businesses unable to implement sophisticated first-party data collection, many advertisers revert to demographic or contextual targeting that may be less relevant than behavioral targeting based on past purchase history and interests. Users who previously benefited from personalization may find their experiences less customized as businesses lose access to detailed user preference data. Website functionality may degrade in limited contexts where legitimate third-party services depended on cookies, though most websites continue functioning normally without access to third-party cookies.
Nevertheless, user sentiment research indicates that most consumers prefer privacy protections over personalization benefits, valuing reduced tracking and surveillance more than they value potential advertising relevance improvements from behavioral targeting. The Cambridge Analytica scandal and other high-profile examples of data misuse and surveillance appear to have shifted consumer preferences toward stronger privacy protections, making consumer demand a significant driver of browser implementations and regulatory frameworks restricting third-party cookies. Users increasingly understand the value of privacy protection and express willingness to tolerate reduced personalization in return for reduced tracking and surveillance.
The Cookie Crossroads: Making Informed Choices
The distinction between first-party and third-party cookies represents far more than a technical classification; it encapsulates fundamental tensions between personalization and privacy, between commercial interests in behavioral targeting and consumer interests in freedom from surveillance, and between innovation in digital services and protection of personal autonomy. First-party cookies, created and controlled by the websites users deliberately visit, enable functionality that consumers generally accept and even appreciate, allowing seamless user experiences with remembered preferences and login states. Third-party cookies, placed by external entities for tracking and targeting purposes, represent the infrastructure that has enabled increasingly sophisticated behavioral surveillance, raising profound privacy concerns that have motivated regulatory intervention and technological implementations restricting their use.
The landscape of cookie-based tracking has undergone and continues to undergo fundamental transformation driven by multiple converging forces. Technological advances in browser-based tracking prevention have made third-party cookies increasingly unavailable across the browser ecosystem, with Safari and Firefox blocking them entirely and Chrome allowing user choice. Regulatory frameworks implementing privacy-protective requirements for user consent and transparency have created legal barriers to third-party cookie deployment while generally permitting first-party cookies for essential functionality. Consumer demand for privacy protection and concerns about surveillance have motivated these regulatory and technological changes, reflecting a genuine shift in how society values privacy relative to commercial personalization.
The industry is experiencing rapid migration toward alternative tracking and personalization approaches that do not depend on third-party cookies. First-party data collection through owned channels provides businesses with sustainable sources of customer information that enable personalization and targeting while maintaining privacy compliance and consumer trust. Zero-party data through explicit customer preference collection creates high-value personalization based on direct customer intent rather than inferred behavior. Contextual advertising provides relevance-based targeting without requiring personal data collection or cross-site tracking. Privacy Sandbox APIs and emerging measurement technologies offer pathways to continued advertising effectiveness without the privacy invasiveness of behavioral tracking.
This transition represents not the death of personalization or targeted advertising but rather their evolution toward approaches that respect user privacy and consent while maintaining commercial effectiveness. Sophisticated businesses implementing first-party data strategies, contextual targeting, and advanced measurement approaches are achieving competitive results in post-third-party cookie environments, suggesting that high-quality marketing remains viable without reliance on behavioral surveillance. The transition period creates disruption and challenges for businesses that have not invested in alternative capabilities, but early evidence indicates that these challenges are manageable and that alternative approaches can provide comparable or superior results compared to legacy third-party cookie approaches.
The role of cookies in the digital ecosystem will continue evolving as technology, regulation, and consumer expectations adapt to this new landscape. First-party cookies will likely remain integral to website functionality indefinitely, as their elimination would break essential site features and users generally accept their use for legitimate website operation. Third-party cookies will continue declining in practical utility and prevalence, remaining technically viable in some browsers but increasingly marginal as businesses and regulatory frameworks move away from reliance on them. The net result will be a digital ecosystem with reduced surveillance, greater transparency about data collection, more explicit user control, and more sustainable competitive dynamics based on legitimate value creation rather than information asymmetries about behavioral tracking. For users, this transition offers the prospect of reduced surveillance and greater autonomy in controlling their personal information, though potentially at the cost of somewhat less personalized digital experiences in contexts where personalization depended on undisclosed behavioral tracking.
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