What is the Topics API?

Summary

Topics is a privacy-focused mechanism designed to enable interest-based advertising without relying on third-party cookies or tracking user activity. The API allows web browsers to share general user interests, like tennis or gardening, based on browsing behavior, while maintaining privacy. Topics enables ad tech platforms to select relevant ads without storing sensitive user data or tracking across sites. It includes user controls to block or disable topics entirely, offering a more secure alternative to current tracking methods. This system is part of the broader Privacy Sandbox initiative, promoting user privacy online.

Takeaways

• 😀 Topics is a Privacy Sandbox API that allows browsers to share user interest data for ad selection without using third-party cookies.
• 😀 The Topics API helps deliver interest-based advertising while addressing privacy concerns by using a taxonomy of categories that avoid sensitive topics.
• 😀 The Topics API provides users with simple controls to block specific topics or disable the API entirely, giving them more control over their data.
• 😀 The API records topics based on the hostname of the websites a user visits, using machine learning to classify topics for less popular sites and a curated list for top sites.
• 😀 Topics is a client-side mechanism, meaning the browser stores user interest data directly on the user's device, enhancing privacy compared to third-party data storage.
• 😀 Third-party callers (such as ad tech platforms) can only access topics they've observed for a user, limiting the amount of user data they can access.
• 😀 Callers can mark topics as observed using the Topics JavaScript API or by using request and response headers on fetch requests or iframes.
• 😀 The browser only shares topics observed within the last three weeks and randomizes the selection of up to three topics to further protect user privacy.
• 😀 Topics are recalculated for each top-level domain, ensuring that topics are different across various sites to prevent user identification through consistent topic patterns.
• 😀 The API is designed to gradually evolve, with feedback from the developer community to refine the taxonomy and improve privacy protections.
• 😀 Google Chrome provides developers with tools like the Colab for Topics and demos to experiment with the API and better understand its implementation and capabilities.

Q & A

What is the purpose of the Topics API?

The Topics API allows web browsers to share information about a user's interests with third-party platforms for interest-based advertising, while preserving user privacy by not revealing sensitive browsing activity or using third-party cookies.

How does the Topics API determine a user's interests?

The Topics API determines a user's interests by analyzing the hostnames of the websites they visit. For example, visiting tennis-related pages might result in interests like 'sports' or 'tennis'.

What is the 'taxonomy' in the context of Topics?

The taxonomy is a human-readable list of categories used to classify topics of interest based on a user's browsing activity. It is publicly maintained and avoids sensitive topics, and it can evolve over time with feedback from the web ecosystem.

How does Chrome ensure privacy when using Topics?

Chrome ensures privacy by storing the user's topics on their device, not on third-party servers, and providing users with the ability to block topics or turn off the API entirely. It also doesn't use third-party cookies or track users across sites.

What role do 'callers' play in the Topics API?

Callers are third-party platforms, like ad tech companies, that request access to a user's topics of interest. They can only access topics they have observed through their presence on specific websites, ensuring that no caller has access to topics from other sites.

What mechanisms do callers use to observe topics in the Topics API?

Callers can observe topics using two mechanisms: by embedding an iframe with JavaScript that calls the `document.browsingTopics` API, or by using request and response headers (like `Sec-Browsing-Topics` and `Observe-Browsing-Topics`) in fetch requests or iframes.

How does the Topics API manage user control over their data?

Users can control the Topics API by viewing, blocking specific topics, or turning off the API entirely through Chrome's settings. Websites can also opt out of participating in Topics calculations.

How does the Topics API ensure diversity in the topics shared with callers?

The API shares up to three topics, one for each of the past three weeks of browsing, selected randomly from the top five topics of each week. Additionally, there's a 5% chance that a topic is randomly selected from the entire taxonomy to further enhance privacy.

What happens if a user blocks a topic or turns off Topics in their browser?

If a user blocks a topic or turns off the Topics API in their browser settings, callers will not be able to access those blocked topics. If Topics is entirely turned off, no topics will be shared with third parties.

What is the 'epoch' in the context of the Topics API, and how does it impact topic selection?

An epoch is a time period (currently one week) during which a user's browsing activity is analyzed. The Topics API returns up to three topics, one for each of the last three epochs, randomly selected from the top five topics for each period.