Topics API

Data & Tracking

Also: Privacy Sandbox Topics · Chrome Topics API

What it isChrome's cookieless ad targeting system

How it worksAssigns broad interest topics, not identity

Watch forThird-party cookies are staying after all

StatusLive but sidelined by Google's u-turn

Quick definition

The Topics API is a Chrome browser feature built by Google that assigns users to broad interest categories, like 'fitness' or 'travel', based on their browsing history. It's designed to let advertisers target ads by interest without third-party cookies or individual tracking.

How it varies across Australia

Adoption among Australian advertisers has been cautious. Most media buyers we talk to treat Topics API as a hedge to test rather than a core targeting strategy, largely because Google backed away from forcing third-party cookie deprecation. Expect adoption to track global patterns rather than a distinct Australian trend.

See data and tracking maturity across Australian industries →

What it actually means

The Topics API works like a librarian handing you a genre sticker instead of your borrowing history. Chrome watches which sites you visit, sorts your recent browsing into a small number of broad interest topics from a fixed public list, and hands three of them to advertisers each week. No individual identifiers, no cross-site profile, just a coarse label like 'Outdoor Recreation' or 'Business Software'.

This sits inside Google's wider Privacy Sandbox, a set of proposed replacements for third-party cookies and cross-site tracking pixels. Topics API was meant to replace the interest-based targeting that cookies used to power, while Protected Audience API was meant to replace remarketing.

Here's the complication. Google announced in 2024 that it would not deprecate third-party cookies in Chrome after all, instead giving users a choice. That decision undercut the urgency behind Topics API almost overnight. Advertisers who spent two years preparing cookieless contingency plans now have a browser that still supports the old approach, alongside a new one nobody is required to use. Attribution and segmentation strategies built around Topics API remain relevant for Safari and Firefox users, where third-party cookies are already blocked, but Chrome itself is a moving target.

The Topics API was built for a cookieless world that Google itself decided not to ship.

How it shows up

Topics API shows up in ad platform documentation as a targeting signal option, usually alongside first-party data and contextual targeting rather than replacing them. It appears in browser privacy settings under Chrome's 'Ad privacy' controls, where users can see and remove topics assigned to them. For marketers, it shows up as a line item in privacy-compliant targeting audits and in conversations with agencies about post-cookie contingency planning, most of which have quietly slowed since Google's reversal.

The Australian context

The Privacy Act reforms moving through the Australian Parliament are pushing local advertisers toward interest-based rather than identity-based targeting regardless of what Chrome does. Topics API fits that direction even if its urgency has faded. Businesses building consent management and data layer architecture for the Australian Privacy Principles should treat topic-based signals as one input among several, not a compliance solution on its own.

Where people get this wrong

Assuming Topics API replaces first-party data collection.Topics API gives broad, shared categories to every advertiser bidding on that user. It can't identify your specific customers or support retention marketing the way owned first-party data can.

Building an entire 2024-2025 tracking strategy around imminent cookie deprecation.Google delayed and then abandoned forced deprecation in Chrome. Teams that treated the timeline as fixed spent budget preparing for a change that didn't arrive on schedule.

Treating Topics API results as equivalent across browsers.Topics API only runs in Chrome. Safari and Firefox already block third-party cookies through their own mechanisms, so a unified cross-browser targeting strategy still needs separate approaches for each.

Topics API vs First-Party Data

	Topics API	First-Party Data
Who collects it	The browser, based on general browsing	Your own business, through direct interactions
Level of detail	Broad shared categories	Specific to your actual customers
Ownership	Controlled by Google's browser policy	Owned and controlled by your business
Best used for	Broad prospecting on Chrome	Retention, personalisation and modelling

Common questions

Is the Topics API replacing third-party cookies?

No, not anymore. Google originally built it as a cookie replacement but then reversed its decision to deprecate third-party cookies in Chrome. Topics API still exists and runs, but it now sits alongside cookies rather than replacing them.

Does the Topics API identify individual users?

No. It assigns broad interest categories from a fixed public list, shared with any advertiser bidding on that browsing session. It's designed specifically to avoid the individual-level identification that third-party cookies enabled.

Should Australian businesses build a strategy around it?

Treat it as one signal among several rather than a core strategy. Given Google's reversal on cookie deprecation, first-party data collection and consent-based targeting remain the more durable investments for Australian marketers navigating Privacy Act reforms.

Which browsers support the Topics API?

Only Chrome. Safari and Firefox already block third-party cookies through their own tracking prevention systems and don't participate in Google's Privacy Sandbox initiative, so cross-browser strategies still need separate approaches.

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About New Rebellion

New Rebellion is a marketing intelligence consultancy. We build tools, score Australian businesses on how their marketing actually performs, and publish Debrief every day. This dictionary is part of how we work in the open.

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