From Firefox 109, we intend to ship a feature that partitions Storage in third-party contexts regardless of whether or not the third-party context has Storage Access.
To prevent cross-site tracking, Firefox has partitioned third-party storage and cookies by default. Websites that want to access the unpartitioned storage or cookies can use Storage Access API to acquire Storage Access from the user. However, the scope of the unpartitoning is not clearly defined, and different browsers have distinct behaviors. We would like to align our behavior with other implementations. So, we change to always partition third-party Storage regardless of Storage Acess. The change can help with Web compatibility and not impact user privacy.
Bug 1758737 - [meta] Always Partition Storage
Safari has already implemented permanently partitioned third-party Storage.
Chrome hasn’t implemented this yet, but has plans to partition all its storage APIs.