There are several ways to check if someone else has used your iPhone or has access to your iCloud account. If there's any reason to suspect that an unauthorized person has used your device, or if you need to make sure that nobody else has access to your iPhone, start here. Taking the steps below can determine whether or not anyone besides you can sign into your account, see your location, or browse your personal information.
Apple's Files app is a great tool for organizing and managing your documents, photos, videos and other files from whatever device you are on. When you first start using it you will see that you can save your files locally (on your current device, e.g. your iPhone or iPad) or to iCloud Drive. Of course many of us use third party cloud storage apps like Google Drive, Dropbox, Amazon Drive, OneDrive and so on. These are compatible with Files, but you'll have to link them before you can start using them with the Files app. Here's how to do it on iPhone or iPad:
The ability to synch your Messages (as well as numerous other services) across multiple Apple devices is undoubtably a huge convenience, but also one that could lead to a serious breach of privacy. Obviously nobody wants their private messages accessible to friends, family and co-workers. If you are the type to have your text messages arrive on every Mac that you use, you might want to check which ones you are logged into, as you wouldn't want your messages popping up on a Mac that you share with a roommate, or on an iPad that you left at a friend's house.
Taking stock of monthly subscriptions now and then can save money. After all, why pay for something that's no longer being used? iCloud Drive usage varies widely depending on how the service is being used. If your iCloud subscription exceeds your needs, it's simple to downgrade and reduce the monthly iTunes charges.