Apple's iCloud service provides five gigabytes of free online data storage to anyone with a valid Apple account. These five gigabytes are used to back up Apple device settings, synchronize documents and save iCloud.com emails. To access an iCloud account, the user must first connect to the service using an iOS mobile device, a Mac computer or a Windows computer running iCloud for Windows.
Users purchase additional storage space from the Change Storage Plan section of their iCloud control panel. Mobile iOS devices automatically back up data to iCloud when connected to a Wi-Fi access point. Information such as purchase history from Apple's store, settings, photos and videos are copied to iCloud's servers during this process. Backed-up settings include screen layouts, user preferences and application configurations.
Some information is automatically stored on iCloud and never needs to be backed up. This includes calendars, contact lists, bookmarks and emails. When enabled, the Documents and Data setting in iCloud allows automatic storage of documents.
Individual files of up to 15 gigabytes can be stored in iCloud using iCloud Drive. The iCloud Drive feature is automatically included in iOS 9 and later versions as well as OS X El Capitan. Users of Windows 7 and later versions access iCloud Drive through the iCloud for Windows application.