A First View of Topics API Usage in the Wild

Among several proposals for a privacy-preserving replacement of third-party cookies, Google's new Topics API is widely discussed as a possible solution. Some scepticism still lingers on the new paradigm from researchers and control bodies; however, the industry has started deploying and testing it. This paper measures the current usage of the Topics API in the wild, discovering third parties that started enabling it, the practices they adopt and their interplay with privacy policies and consent acquisition mechanisms.