To improve our testing process, we are creating isolated experiments for each of the origin trial APIs, in addition to the existing unified experiment. The new Topics API isolated experiment will receive 1% of new Stable traffic on top of the existing 5% of Stable traffic from the unified experiment.
The isolated experiment will launch on Monday, March 13, 2023, and you will begin to receive a total of 6% of the Stable traffic for Topics (5% from the unified experiment and 1% from the new isolated experiment).
We initially communicated that we will begin the Topics API isolated experiment on Monday, March 13, 2023, but the new experiments will now begin on Thursday, March 16, 2023 due to the additional time needed for setting up the experiments.
For a deeper dive into these changes, please see the Relevance and measurement unified origin trial article on the Chrome blog. If you have any questions on this change, please file an issue in the Topics GitHub repository.