It isn't based on a list of login providers, instead there are temporary heuristics: https://hacks.mozilla.org/2021/02/introducing-state-partitioning/ https://h

It isn't based on a list of login providers, instead there are temporary heuristics: https://hacks.mozilla.org/2021/02/introducing-state-partitioning/ https://hacks.mozilla.org/2021/02/introducing-state-partitio... In the Firefox storage access policy, we have defined several heuristics to address Web compatibility issues. The heuristics are designed to catch the most common scenarios of using third-party storage on the web (outside of tracking) and allow storage access in order to make websites continue normally. For example, in Single-Sign-On flows it is common to open a popup that allows the user to sign in, and transmit that sign-in information back to the website that opened the popup. Firefox will detect this case and automatically grant storage access. Note that these heuristics are not designed for the long term. Using the Storage Access API is the recommended solution for websites that need unpartitioned access. We will continually evaluate the necessity of the restrictions and remove them as appropriate. Therefore, developers should not rely on them now or in the future.