Hi Ziqiao, That would be fine, I am actually not interested in sharing a container between the main app and extension. The only reason I even started interacting with the data in the main app was because I couldn't understand why the extension wasn't synchronizing. With the main app I verified that everything about cloudkit was set up correctly. And then when I put them in the same group, they started sharing a container, and I am sure the extension is reading/writing correctly to the container. However, if I disable all interaction with the container in the main app, the records from the extension are never synchronized with cloudkit. Is there some reason for the safari extension to be blocked from synchronizing?