Third-party cookies have been dying in slow motion for years. Safari blocked them by default in 2020. Firefox followed. Chrome — which accounts for roughly 65% of browser usage in Australia — has been rolling out restrictions since 2024 under its Privacy Sandbox initiative.

If you’re an Australian marketer who hasn’t yet adapted, you’re running out of runway. The tracking infrastructure that powered programmatic advertising, retargeting campaigns, and cross-site audience building for the past two decades is fundamentally changing. Not might change. Is changing. Right now.

What’s Actually Going Away

Third-party cookies are small data files placed on a user’s browser by domains other than the one they’re visiting. When you visit an online shoe store and then see shoe ads following you across news sites and social media, that’s third-party cookies at work.

They’ve been the backbone of digital advertising targeting and measurement. Advertising platforms used them to build detailed behavioural profiles across the web, enabling precise audience targeting and attribution tracking.

What’s not going away: first-party cookies. The cookies set by the website you’re actually visiting — for things like keeping you logged in, remembering your shopping cart, and tracking on-site behaviour — remain fully functional. The distinction is critical because it defines where the line is being drawn.

Why This Is Happening

The shift isn’t arbitrary. It’s a response to genuine privacy concerns and regulatory pressure.

Consumers have grown increasingly uncomfortable with the extent of cross-site tracking. Research from the Office of the Australian Information Commissioner found that 84% of Australians consider the protection of their personal information an important concern, and 69% are uncomfortable with targeted advertising based on their browsing history.

The European GDPR, California’s CCPA, and Australia’s evolving Privacy Act reforms all reflect a regulatory trend toward stronger data protection. Browser makers have responded by building privacy protections into their products rather than waiting for legislation to force their hand.

The Impact on Digital Advertising

For marketers relying on third-party cookie-based targeting, the impacts are substantial.

Retargeting campaigns lose their primary mechanism. The ability to show ads to people who visited your website but didn’t convert — one of the most effective advertising tactics — depends on third-party cookies. Without them, you can’t follow users across sites with standard display advertising.

Lookalike audience building becomes harder. Platforms like Meta and Google used cross-site behavioural data to build audiences that resemble your existing customers. With less behavioural data available, these lookalike models become less precise.

Cross-device tracking deteriorates. Third-party cookies helped connect user behaviour across desktop and mobile browsers (though imperfectly). Without them, understanding the cross-device customer journey gets significantly harder.

Attribution and measurement face challenges. Multi-touch attribution models that tracked a user’s journey from first ad exposure to conversion across multiple sites relied heavily on third-party cookies. Measuring true campaign ROI becomes more complex.

What’s Replacing Cookies

Several alternatives are emerging, though none fully replicate what third-party cookies provided.

Google’s Privacy Sandbox offers a set of APIs designed to enable advertising targeting and measurement without individual-level cross-site tracking. The Topics API infers user interests from browsing history and shares them with advertisers in a privacy-preserving way. The Attribution Reporting API provides conversion measurement without exposing individual user journeys. It’s a compromise — less precise than cookies, more privacy-respecting.

First-party data strategies are the most important adaptation. Building direct relationships with customers — through email lists, loyalty programs, app installations, and account registrations — gives you owned data that doesn’t depend on third-party infrastructure. A customer who’s given you their email address and purchase history provides richer data than any cookie profile.

Server-side tracking moves analytics processing from the user’s browser to your server, bypassing browser-level cookie restrictions. Google Tag Manager offers server-side tagging capabilities. It requires more technical setup but provides more reliable data collection.

Contextual advertising is experiencing a renaissance. Rather than targeting based on who the user is (behavioural targeting), contextual advertising targets based on what content the user is viewing. An ad for running shoes appears on an article about marathon training. It’s less precise than behavioural targeting but faces no privacy concerns.

Data clean rooms enable advertisers and publishers to match their first-party data sets for targeting and measurement without sharing raw data with each other. Platforms like LiveRamp and InfoSum facilitate this. It’s more complex than cookie-based targeting but preserves privacy while enabling useful audience insights.

What Australian Marketers Should Do Now

Audit your current cookie dependency. Understand which of your marketing activities rely on third-party cookies. If your retargeting campaigns, audience building, and attribution models are all cookie-dependent, you need to act urgently.

Invest in first-party data collection. Make it easy and valuable for customers to share their information directly with you. Email signup forms, loyalty programs, quiz funnels, gated content — anything that creates a direct data relationship. First-party data is more valuable than cookie data ever was because it comes with explicit consent and is under your control.

Implement server-side tracking. Move your analytics infrastructure to server-side where possible. It’s more resilient to browser changes and provides better data quality.

Test contextual advertising. Run contextual campaigns alongside your behavioural campaigns and compare performance. Many advertisers find that well-placed contextual ads perform comparably to behavioural targeting, sometimes better.

Update your measurement framework. Accept that perfect attribution is gone. Multi-touch attribution models based on user-level tracking will become less reliable. Marketing mix modelling and incrementality testing — statistical approaches that measure campaign impact at an aggregate level — are becoming more important.

The Silver Lining

The cookie apocalypse is forcing marketers to build better, more sustainable customer relationships. The companies that win in a post-cookie world are those with strong brands, engaged audiences, and rich first-party data — not those with the most sophisticated tracking pixels.

That’s not a bad outcome. The era of silent surveillance-based marketing was convenient for advertisers but uncomfortable for consumers. What’s replacing it requires more effort but creates more genuine value on both sides of the transaction.

The marketers who adapt earliest will have a significant advantage over those who wait until the last cookie crumbles.