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Building a privacy-first future for web advertising

January 25th, 2021

Advertising is essential to keeping the web open for everyone, but the web ecosystem is at risk if privacy practices do not keep up with changing expectations. ​People want assurances that their identity and information are safe as they browse the web. That’s why Chrome introduced the Privacy Sandbox and, today, shared progress on their path to eliminate third-party cookies by replacing them with viable privacy-first alternatives, developed alongside ecosystem partners, that will help publishers and advertisers succeed while also protecting people’s privacy as they move across the web.

It might be hard to imagine how advertising on the web could be relevant, and accurately measured, without ​third-party cookies. When the Privacy Sandbox technology for interest-based advertising (FLoC) was first proposed last year, we started with the idea that groups of people with common interests could replace individual identifiers. Today, we’re releasing new data showing how this innovation can deliver results nearly as effective as cookie-based approaches.​ Technology advancements such as FLoC, along with similar promising efforts in areas like measurement, fraud protection, and anti-fingerprinting, are the future of web advertising — and the Privacy Sandbox will power our web products in a post-third-party cookie world.

Interest-based advertising

Federated Learning of Cohorts (FLoC) proposes a new way for businesses to reach people with relevant content and ads by clustering large groups of people with similar interests. This approach effectively hides individuals “in the crowd” and uses on-device processing to keep a person’s web history private on the browser.

By creating simulations based on the principles defined in Chrome’s FLoC proposal, Google’s ads teams have tested this privacy-first alternative to third-party cookies. Results indicate that when it comes to generating interest-based audiences, FLoC can provide an effective replacement signal for third-party cookies. Our tests of FLoC to reach in-market and affinity Google Audiences show that advertisers can expect to see at least 95% of the conversions per dollar spent when compared to cookie-based advertising. The specific result depends on the strength of the clustering algorithm that FLoC uses and the type of audience being reached.

We’re encouraged by what we’ve observed and the value that this solution offers to users, publishers and advertisers. Chrome intends to make FLoC-based cohorts available for public testing through origin trials with its next release in March and we expect to begin testing FLoC-based cohorts with advertisers in Google Ads in Q2. If you’d like to get a head start, you can run your own simulations (as we did) based on the principles outlined in this FLoC whitepaper.

Audience creation

The Privacy Sandbox also includes proposals for how marketers can create and deploy their own audiences, without the use of third-party cookies. One example is when advertisers want to reach prior visitors to their website via remarketing.

Over the last year, several members of the ad tech community have offered input for how this might work, including proposals from Criteo, NextRoll, Magnate, and RTB House. Chrome has published a new proposal called FLEDGE that expands on a previous Chrome proposal (called TURTLEDOVE) and takes into account the industry feedback they’ve heard, including the idea of using a “trusted server” — as defined by compliance with certain principles and policies — that’s specifically designed to store information about a campaign’s bids and budgets. Chrome intends to make FLEDGE available for testing through origin trials later this year with the opportunity for ad tech companies to try using the API under a “bring your own server” model.

While proposals such as FLoC and FLEDGE explore privacy-preserving alternatives for reaching relevant audiences, there’s also work being done to help buyers decide how much to bid for ads seen by these audiences. We invite ad exchanges, demand-side platforms, and advertisers to begin experimenting with the technology in the Privacy Sandbox. Feedback from these tests will help ensure that ad auctions will continue to function seamlessly when third-party cookies are deprecated.

Conversion measurement

Chrome has proposed a number of technologies within the Privacy Sandbox that would allow marketers, and partners working on their behalf, to measure campaign performance without third-party cookies. These proposals protect consumer privacy while supporting key advertiser requirements, such as event-level reporting that enables bidding models to recognize patterns in the data, and aggregate-level reporting which delivers accurate measurement over groups of users.

By using privacy-preserving techniques like aggregating information, adding noise, and limiting the amount of data that gets sent from the device, the proposed APIs report conversions in a way that protects user privacy. For example, an event-level iteration of the API is currently available in origin trials for measuring click-through conversions. It protects privacy by introducing noise and limiting the bits of conversion data that the API can send at a time. As a result, advertisers will have to prioritize which conversions are most important for their reporting needs.

Over the coming months, Google’s ads teams will continue evaluating how the proposed conversion measurement APIs can be used alongside Google’s measurement products to support use cases such as reporting view-through conversions, determining incrementality and reach as well as performing attribution. We recommend customers implement sitewide tagging with the global site tag or Google Tag Manager in order to minimize disruptions during this time. More decisions will have to be made before a prototype is built — including what the right level of noise should be and what’s the minimum number of conversions to include when sending an aggregate-level report — so we invite ad tech companies, publishers and advertisers to get involved in these discussions within the public forums.

Ad fraud prevention

The health of the ad-supported web depends on companies being able to distinguish actual visitors from fraudulent traffic. That’s why Chrome opened the Trust Token API for testing last July to help verify authentic traffic without exposing people’s identities in the process. And today, Chrome shared plans to start an origin trial in March with their next release to support a new type of Trust Token issuer that would improve the detection of fraud on mobile devices while safeguarding user privacy. Google’s ads teams will then start testing this feature with trusted users on mobile, and share feedback within the public forums based on the results.

Anti-fingerprinting

An important goal of the Privacy Sandbox is developing technology to protect people from opaque or hidden techniques that share data about individual users and allow them to be tracked in a covert manner. One such tactic involves using a device’s IP address to try and identify someone without their knowledge or ability to opt-out. Chrome recently published a new proposal, Gnatcatcher, for how someone’s IP address might be masked to protect that person’s identity without interfering with a website’s normal operations. This proposal will continue to be refined based on feedback from the web community.

The future of privacy on the web

Thanks to the initial FLoC results, the ongoing development of the APIs, and encouraging dialogue with the industry, we are more confident than ever that the Privacy Sandbox is the best path forward to improve privacy for web users while ensuring publishers can earn what they need to fund great content and advertisers can reach the right people for their products. For Google’s ads teams, the Privacy Sandbox technologies represent the future of how our ads and measurement products will work on the web. We encourage others to join us in defining this new approach which will create better experiences for consumers while providing more durable solutions for the ads industry.

As we move forward in 2021, you can expect to hear more about the progress being made in the Privacy Sandbox, including more opportunities for you to begin testing these new technologies in your campaigns. So, stay engaged in the public discussions about the Privacy Sandbox proposals in forums like the W3C’s Improving Web Advertising Business Group, or work with your technology partners to evaluate and experiment with the proposals that are already in origin trials. Together, we can reshape the web so that it works better for everyone.