What can be used to transfer information between two applications working with the same account?

To transfer information between two applications operating with the same account on iOS, several approaches can be used:

• App Groups and Shared Container: allow applications from the same group to share files and data through a common container.
• UIPasteboard: a shared clipboard that can be used to transfer small amounts of data.
• URL Schemes (Custom URL Schemes): to launch one application from another with parameter passing.
• NSUserDefaults with App Groups: for storing and reading shared settings.

For example, using App Groups allows applications to read and write data to a shared directory:

let sharedDefaults = UserDefaults(suiteName: "group.com.example.myapp")
sharedDefaults?.set("value", forKey: "key")

This is the safest and recommended way to exchange data between applications of the same developer on iOS.