I believe tropic interest is calculated locally by the (Google) browser, though it might be repeatable on the Google server side for users syncing their browsin

I believe tropic interest is calculated locally by the (Google) browser, though it might be repeatable on the Google server side for users syncing their browsing history to a Google account. The Topics API itself only returns up to three topic IDs to websites, not 500 bits for all topics. But that still gives trackers up to 500 * 499 * 498 (124,251,000) topic combinations that can be paired with other fingerprintable user information like GeoIP, language, browser version, and operating system.