The ICloud ecosystem is complicated, and it is difficult to know how much of your data is safe in the "cloud" and synchronized over your devices. We go through the process of configuring and explaining what each function does.
How to log in to iCloud
When you first set up your Mac, you should be prompted to sign in with an iCloud account. If you have already set it up, you are good to go, but if you are not logged in, you must log in from the iCloud settings.
Open the System Preferences app ̵
These are the iCloud settings. If you are not logged in, you will see this login screen.
If you already have an Apple ID from an iPhone or iPad, make sure you use the same one for your Mac, otherwise nothing will sync between your devices. If you need to create a new account, click "Create Apple ID" at the bottom to sign up.
You can sign up with your own email address, such as a Gmail account, or you can create a new @ icloud.com email address. Either will create a new iCloud account, which you can use on any device you want.
What syncs automatically?
The main feature of iCloud keeps your critical personal information synchronized across your devices (and backed up in the cloud). Most iCloud features synchronize the following data across all your connected devices from the box:
- Your contacts
- Calendar appointments and reminders
- Safari data, including passwords, open pages, and browsing history
- HomeKit access  Notes you have made in the Notes app
- Mail that you have sent and received, as well as drafts
You should not have to worry about any of these as long as you are logged in and the option is selected in the iCloud settings on your Mac. Make sure the options are also enabled in the iCloud settings on your iOS devices, and any other device you have logged into the same iCloud account, or you may have problems.
] The most important thing to note with pictures is that there are two methods for backing them up. The first, "iCloud Photos", only stores every photo you take in iCloud and synchronizes over devices. If the device is broken, you can enable "iCloud Photos" on a new device and download all your images in iCloud.
"My Photo Stream" is different and only stores the latest images for a month to give your other devices time to synchronize. That means if you take a picture on your iPhone and don't use your iPad for a while, your photos won't sync with the iPad. Also, nothing more than the last month is backed up with images, so if you lose your device without "iCloud Photos" being enabled, you will not be able to get your photos back.
There is still a use for "My Photo Stream", but when you store every photo you take iCloud you will quickly fill in all 5 GB of free storage that comes with iCloud. If you have two devices you use regularly, like a MacBook and an iPhone, which only has "My Photo Stream" enabled, you can save a lot of space while your photos are backed up on your MacBook. Just don't break them both at the same time.
iMessage will not be enabled by default, but all that is required is to log in when you start the app for the first time. Just make sure you sign in with the same account you use on your iPhone or iPad, and make sure iMessage is enabled on all your devices.
This will not sync any old messages you may have on your Mac. For that you must enable "Messages in iCloud". Once you have logged in, click on "Messages" in the top menu bar and open the settings.
 Open the blue "iMessage" tab at the top and make sure "Enable iCloud Messages" is selected.
As long as this option is enabled, your messages should be synchronized regardless of when they were sent. Again, make sure the option is enabled on all of your devices for it to work properly.
iCloud Drive is used for everything else. TextEdit documents, your books, your system settings, Automator scripts, the entire kitchen tray. If it's a document you've made in a built-in Apple app, it's probably synced here.
By default, iCloud Drive also stores folders for desktops and documents, which can be very large. You can quickly fill in your iCloud account if you keep these. And if you do not pay Apple $ 0.99 a month for their 50 GB iCloud plan, you will be pinged with messages in a few hours saying you should buy more space.
 However, you cannot simply uncheck "Desktop and Document Folders" to turn off iCloud Drive, because the process of disabling it is far harder than it should be. You can read our guide on disabling iCloud Drive without inadvertently deleting your data.
While iCloud Drive takes up a lot of space in iCloud, it is a useful feature if you choose to pay for more storage. It saves all the desktop and document folders to iCloud, and then removes old files that you do not use from your MacBook to save space. When you need the file again, you can download it from iCloud. So if you have an old MacBook with a small hard drive, you can pay a few dollars a month to give it a little more breathing space.